From c2fbbf4d66fcc61a87fdc6675cdb4432d7ef7779 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 16:08:52 +0200
Subject: [PATCH 01/12] Delete VectorOfVariables constraint when the function
 matches

---
 src/Utilities/functions.jl          |  12 +--
 src/Utilities/mockoptimizer.jl      |  13 +++
 src/Utilities/model.jl              | 161 +++++++++++++++++++---------
 src/Utilities/sets.jl               |   4 +-
 src/Utilities/universalfallback.jl  | 129 +++++++++++++++-------
 test/Utilities/model.jl             |  20 +++-
 test/Utilities/universalfallback.jl |  60 +++++++++++
 7 files changed, 298 insertions(+), 101 deletions(-)

diff --git a/src/Utilities/functions.jl b/src/Utilities/functions.jl
index b1a1ac7726..d46fc18ad1 100644
--- a/src/Utilities/functions.jl
+++ b/src/Utilities/functions.jl
@@ -460,25 +460,25 @@ function _rmvar(vis_or_terms::Vector, vi)
 end
 
 """
-    removevariable(f::AbstractFunction, vi::VariableIndex)
+    remove_variable(f::AbstractFunction, vi::VariableIndex)
 
 Return a new function `f` with the variable vi removed.
 """
-function removevariable end
-function removevariable(f::MOI.SingleVariable, vi::MOI.VariableIndex)
+function remove_variable end
+function remove_variable(f::MOI.SingleVariable, vi::MOI.VariableIndex)
     if f.variable == vi
         error("Cannot remove variable from a `SingleVariable` function of the",
               " same variable.")
     end
     return f
 end
-function removevariable(f::VVF, vi)
+function remove_variable(f::VVF, vi)
     VVF(_rmvar(f.variables, vi))
 end
-function removevariable(f::Union{SAF, VAF}, vi)
+function remove_variable(f::Union{SAF, VAF}, vi)
     typeof(f)(_rmvar(f.terms, vi), MOI.constant(f))
 end
-function removevariable(f::Union{SQF, VQF}, vi)
+function remove_variable(f::Union{SQF, VQF}, vi)
     terms = _rmvar.((f.affine_terms, f.quadratic_terms), Ref(vi))
     typeof(f)(terms..., MOI.constant(f))
 end
diff --git a/src/Utilities/mockoptimizer.jl b/src/Utilities/mockoptimizer.jl
index 73287726b1..0af8212893 100644
--- a/src/Utilities/mockoptimizer.jl
+++ b/src/Utilities/mockoptimizer.jl
@@ -385,6 +385,19 @@ function MOI.delete(mock::MockOptimizer, index::MOI.VariableIndex)
     MOI.delete(mock.inner_model, xor_index(index))
     delete!(mock.varprimal, index)
 end
+function MOI.delete(mock::MockOptimizer, indices::Vector{MOI.VariableIndex})
+    if !mock.delete_allowed && !isempty(indices)
+        throw(MOI.DeleteNotAllowed(first(indices)))
+    end
+    for index in indices
+        # The index thrown by `mock.inner_model` would be xored
+        MOI.throw_if_not_valid(mock, index)
+    end
+    MOI.delete(mock.inner_model, xor_index.(indices))
+    for index in indices
+        delete!(mock.varprimal, index)
+    end
+end
 function MOI.delete(mock::MockOptimizer, index::MOI.ConstraintIndex)
     if !mock.delete_allowed
         throw(MOI.DeleteNotAllowed(index))
diff --git a/src/Utilities/model.jl b/src/Utilities/model.jl
index 9d69737826..402d6402d3 100644
--- a/src/Utilities/model.jl
+++ b/src/Utilities/model.jl
@@ -103,7 +103,7 @@ function MOI.add_variables(model::AbstractModel, n::Integer)
 end
 
 """
-    removevariable(f::MOI.AbstractFunction, s::MOI.AbstractSet, vi::MOI.VariableIndex)
+    remove_variable(f::MOI.AbstractFunction, s::MOI.AbstractSet, vi::MOI.VariableIndex)
 
 Return a tuple `(g, t)` representing the constraint `f`-in-`s` with the
 variable `vi` removed. That is, the terms containing the variable `vi` in the
@@ -111,46 +111,74 @@ function `f` are removed and the dimension of the set `s` is updated if
 needed (e.g. when `f` is a `VectorOfVariables` with `vi` being one of the
 variables).
 """
-removevariable(f, s, vi::VI) = removevariable(f, vi), s
-function removevariable(f::MOI.VectorOfVariables, s, vi::VI)
-    g = removevariable(f, vi)
+remove_variable(f, s, vi::VI) = remove_variable(f, vi), s
+function remove_variable(f::MOI.VectorOfVariables, s, vi::VI)
+    g = remove_variable(f, vi)
     if length(g.variables) != length(f.variables)
-        t = updatedimension(s, length(g.variables))
+        t = update_dimension(s, length(g.variables))
     else
         t = s
     end
     return g, t
 end
-function _removevar!(constrs::Vector, vi::VI)
+function _remove_variable(constrs::Vector, vi::VI)
     for i in eachindex(constrs)
         ci, f, s = constrs[i]
-        constrs[i] = (ci, removevariable(f, s, vi)...)
+        constrs[i] = (ci, remove_variable(f, s, vi)...)
     end
     return CI{MOI.SingleVariable}[]
 end
-function _removevar!(constrs::Vector{<:ConstraintEntry{MOI.SingleVariable}},
-                     vi::VI)
-    # If a variable is removed, the SingleVariable constraints using this variable
-    # need to be removed too
-    rm = CI{MOI.SingleVariable}[]
+function _vector_of_variables_with(::Vector, ::Union{VI, MOI.Vector{VI}})
+    return CI{MOI.VectorOfVariables}[]
+end
+function throw_delete_variable_in_vov(vi::VI)
+    message = string("Cannot delete variable as it is constrained with other",
+                     " other variables in a `MOI.VectorOfVariables`.")
+    throw(MOI.DeleteNotAllowed(vi, message))
+end
+function _vector_of_variables_with(
+    constrs::Vector{<:ConstraintEntry{MOI.VectorOfVariables}}, vi::VI)
+    rm = CI{MOI.VectorOfVariables}[]
     for (ci, f, s) in constrs
-        if f.variable == vi
-            push!(rm, ci)
+        if vi in f.variables
+            if length(f.variables) > 1
+                # If `s isa DimensionUpdatableSets` then the variable will be
+                # removed in `_remove_variable`.
+                if !(s isa DimensionUpdatableSets)
+                    throw_delete_variable_in_vov(vi)
+                end
+            else
+                push!(rm, ci)
+            end
         end
     end
     return rm
 end
-function MOI.delete(model::AbstractModel, vi::VI)
-    if !MOI.is_valid(model, vi)
-        throw(MOI.InvalidIndex(vi))
+function _vector_of_variables_with(
+    constrs::Vector{<:ConstraintEntry{MOI.VectorOfVariables}},
+    vis::Vector{VI}
+)
+    rm = CI{MOI.VectorOfVariables}[]
+    for (ci, f, s) in constrs
+        if vis == f.variables
+            push!(rm, ci)
+        end
     end
-    model.objective = removevariable(model.objective, vi)
-    # `ci_to_remove` is the list of indices of the `SingleVariable` constraints
-    # of `vi`
-    ci_to_remove = broadcastvcat(constrs -> _removevar!(constrs, vi), model)
-    for ci in ci_to_remove
+    return rm
+end
+function MOI.delete(model::AbstractModel{T}, vi::VI) where T
+    MOI.throw_if_not_valid(model, vi)
+    model.objective = remove_variable(model.objective, vi)
+    # If a variable is removed, the `VectorOfVariables` constraints using this
+    # variable only need to be removed too. `vov_to_remove` is the list of
+    # indices of the `VectorOfVariables` constraints of `vi`.
+    vov_to_remove = broadcastvcat(constrs -> _vector_of_variables_with(constrs, vi), model)
+    for ci in vov_to_remove
         MOI.delete(model, ci)
     end
+    # `VectorOfVariables` constraints with non-`DimensionUpdatableSets` were
+    # either deleted or an error was thrown. The rest is modified now.
+    broadcastcall(constrs -> _remove_variable(constrs, vi), model)
     model.single_variable_mask[vi.value] = 0x0
     if model.variable_indices === nothing
         model.variable_indices = Set(MOI.get(model,
@@ -158,8 +186,24 @@ function MOI.delete(model::AbstractModel, vi::VI)
     end
     delete!(model.variable_indices, vi)
     model.name_to_var = nothing
-    if haskey(model.var_to_name, vi)
-        delete!(model.var_to_name, vi)
+    delete!(model.var_to_name, vi)
+    model.name_to_con = nothing
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.EqualTo{T}}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.GreaterThan{T}}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.LessThan{T}}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.Interval{T}}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.Integer}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.ZeroOne}(vi.value))
+end
+function MOI.delete(model::AbstractModel, vis::Vector{VI})
+    # Delete `VectorOfVariables(vis)` constraints as otherwise, it will error
+    # when removing variables one by one.
+    vov_to_remove = broadcastvcat(constrs -> _vector_of_variables_with(constrs, vis), model)
+    for ci in vov_to_remove
+        MOI.delete(model, ci)
+    end
+    for vi in vis
+        MOI.delete(model, vi)
     end
 end
 
@@ -214,26 +258,48 @@ function MOI.set(model::AbstractModel, ::MOI.VariableName, vi::VI, name::String)
 end
 MOI.get(model::AbstractModel, ::MOI.VariableName, vi::VI) = get(model.var_to_name, vi, EMPTYSTRING)
 
+"""
+    build_name_to_var_map(con_to_name::Dict{MOI.VariableIndex, String})
+
+Create and return a reverse map from name to variable index, given a map from
+variable index to name. The special value `MOI.VariableIndex(0)` is used to
+indicate that multiple variables have the same name.
+"""
+function build_name_to_var_map(var_to_name::Dict{VI, String})
+    name_to_var = Dict{String, VI}()
+    for (var, var_name) in var_to_name
+        if haskey(name_to_var, var_name)
+            # 0 is a special value that means this string does not map to
+            # a unique variable name.
+            name_to_var[var_name] = VI(0)
+        else
+            name_to_var[var_name] = var
+        end
+    end
+    return name_to_var
+end
+
+function throw_multiple_name_error(::Type{MOI.VariableIndex}, name::String)
+    error("Multiple variables have the name $name.")
+end
+function throw_multiple_name_error(::Type{<:MOI.ConstraintIndex}, name::String)
+    error("Multiple constraints have the name $name.")
+end
+function throw_if_multiple_with_name(::Nothing, ::String) end
+function throw_if_multiple_with_name(index::MOI.Index, name::String)
+    if iszero(index.value)
+        throw_multiple_name_error(typeof(index), name)
+    end
+end
+
 function MOI.get(model::AbstractModel, ::Type{VI}, name::String)
     if model.name_to_var === nothing
         # Rebuild the map.
-        model.name_to_var = Dict{String, VI}()
-        for (var, var_name) in model.var_to_name
-            if haskey(model.name_to_var, var_name)
-                # -1 is a special value that means this string does not map to
-                # a unique variable name.
-                model.name_to_var[var_name] = VI(-1)
-            else
-                model.name_to_var[var_name] = var
-            end
-        end
+        model.name_to_var = build_name_to_var_map(model.var_to_name)
     end
     result = get(model.name_to_var, name, nothing)
-    if result == VI(-1)
-        error("Multiple variables have the name $name.")
-    else
-        return result
-    end
+    throw_if_multiple_with_name(result, name)
+    return result
 end
 
 function MOI.get(model::AbstractModel, ::MOI.ListOfVariableAttributesSet)::Vector{MOI.AbstractVariableAttribute}
@@ -252,14 +318,14 @@ MOI.get(model::AbstractModel, ::MOI.ConstraintName, ci::CI) = get(model.con_to_n
 
 Create and return a reverse map from name to constraint index, given a map from
 constraint index to name. The special value
-`MOI.ConstraintIndex{Nothing, Nothing}(-1)` is used to indicate that multiple
+`MOI.ConstraintIndex{Nothing, Nothing}(0)` is used to indicate that multiple
 constraints have the same name.
 """
 function build_name_to_con_map(con_to_name::Dict{CI, String})
     name_to_con = Dict{String, CI}()
     for (con, con_name) in con_to_name
         if haskey(name_to_con, con_name)
-            name_to_con[con_name] = CI{Nothing, Nothing}(-1)
+            name_to_con[con_name] = CI{Nothing, Nothing}(0)
         else
             name_to_con[con_name] = con
         end
@@ -274,9 +340,8 @@ function MOI.get(model::AbstractModel, ConType::Type{<:CI}, name::String)
         model.name_to_con = build_name_to_con_map(model.con_to_name)
     end
     ci = get(model.name_to_con, name, nothing)
-    if ci == CI{Nothing, Nothing}(-1)
-        error("Multiple constraints have the name $name.")
-    elseif ci isa ConType
+    throw_if_multiple_with_name(ci, name)
+    if ci isa ConType
         return ci
     else
         return nothing
@@ -446,14 +511,10 @@ function _delete_constraint(model::AbstractModel, ci::CI)
     model.constrmap[ci.value] = 0
 end
 function MOI.delete(model::AbstractModel, ci::CI)
-    if !MOI.is_valid(model, ci)
-        throw(MOI.InvalidIndex(ci))
-    end
+    MOI.throw_if_not_valid(model, ci)
     _delete_constraint(model, ci)
     model.name_to_con = nothing
-    if haskey(model.con_to_name, ci)
-        delete!(model.con_to_name, ci)
-    end
+    delete!(model.con_to_name, ci)
 end
 
 function MOI.modify(model::AbstractModel, ci::CI, change::MOI.AbstractFunctionModification)
diff --git a/src/Utilities/sets.jl b/src/Utilities/sets.jl
index 9b526f66d5..4a5cc367e2 100644
--- a/src/Utilities/sets.jl
+++ b/src/Utilities/sets.jl
@@ -3,11 +3,11 @@ const DimensionUpdatableSets = Union{MOI.Reals,
                                      MOI.Nonnegatives,
                                      MOI.Nonpositives}
 """
-    updatedimension(s::AbstractVectorSet, newdim)
+    update_dimension(s::AbstractVectorSet, newdim)
 
 Returns a set with the dimension modified to `newdim`.
 """
-function updatedimension(::S, newdim) where S<:DimensionUpdatableSets
+function update_dimension(::S, newdim) where S<:DimensionUpdatableSets
     S(newdim)
 end
 
diff --git a/src/Utilities/universalfallback.jl b/src/Utilities/universalfallback.jl
index 46ce06ace4..c9550bc71f 100644
--- a/src/Utilities/universalfallback.jl
+++ b/src/Utilities/universalfallback.jl
@@ -73,30 +73,86 @@ function MOI.delete(uf::UniversalFallback, ci::CI{F, S}) where {F, S}
             throw(MOI.InvalidIndex(ci))
         end
         delete!(uf.constraints[(F, S)], ci)
-        if haskey(uf.con_to_name, ci)
-            delete!(uf.con_to_name, ci)
-        end
+        delete!(uf.con_to_name, ci)
         uf.name_to_con = nothing
     end
     for d in values(uf.conattr)
         delete!(d, ci)
     end
 end
+function _remove_variable(uf::UniversalFallback,
+                          constraints::Dict{<:CI{MOI.SingleVariable}}, vi::VI)
+    to_delete = keytype(constraints)[]
+    for (ci, constraint) in constraints
+        f::MOI.SingleVariable = constraint[1]
+        if f.variable == vi
+            push!(to_delete, ci)
+        end
+    end
+    MOI.delete(uf, to_delete)
+end
+function _remove_variable(uf::UniversalFallback,
+                          constraints::Dict{CI{MOI.VectorOfVariables, S}},
+                          vi::VI) where S
+    to_delete = keytype(constraints)[]
+    for (ci, constraint) in constraints
+        f::MOI.VectorOfVariables, s = constraint
+        if vi in f.variables
+            if length(f.variables) > 1
+                if S <: MOIU.DimensionUpdatableSets
+                    constraints[ci] = remove_variable(f, s, vi)
+                else
+                    throw_delete_variable_in_vov(vi)
+                end
+            else
+                push!(to_delete, ci)
+            end
+        end
+    end
+    MOI.delete(uf, to_delete)
+end
+function _remove_variable(::UniversalFallback, constraints::Dict{<:CI}, vi::VI)
+    for (ci, constraint) in constraints
+        f, s = constraint
+        constraints[ci] = remove_variable(f, s, vi)
+    end
+end
+function _remove_vector_of_variables(
+    uf::UniversalFallback, constraints::Dict{<:CI{MOI.VectorOfVariables}},
+    vis::Vector{VI}
+)
+    to_delete = keytype(constraints)[]
+    for (ci, constraint) in constraints
+        f::MOI.VectorOfVariables = constraint[1]
+        if vis == f.variables
+            push!(to_delete, ci)
+        end
+    end
+    MOI.delete(uf, to_delete)
+end
+function _remove_vector_of_variables(
+    ::UniversalFallback, ::Dict{<:CI}, ::Vector{VI})
+end
 function MOI.delete(uf::UniversalFallback, vi::VI)
     MOI.delete(uf.model, vi)
     for d in values(uf.varattr)
         delete!(d, vi)
     end
-    for (FS, constraints) in uf.constraints
-        for (ci, constraint) in constraints
-            f, s = constraint
-            if f isa MOI.SingleVariable
-                if f.variable == vi
-                    delete!(constraints, ci)
-                end
-            else
-                constraints[ci] = removevariable(f, s, vi)
-            end
+    for (_, constraints) in uf.constraints
+        _remove_variable(uf, constraints, vi)
+    end
+end
+function MOI.delete(uf::UniversalFallback, vis::Vector{VI})
+    MOI.delete(uf.model, vis)
+    for d in values(uf.varattr)
+        for vi in vis
+            delete!(d, vi)
+        end
+    end
+    for (_, constraints) in uf.constraints
+        _remove_vector_of_variables(uf, constraints, vis)
+        for vi in vis
+            _remove_variable(uf, constraints, vi)
         end
     end
 end
@@ -214,47 +270,38 @@ function MOI.get(uf::UniversalFallback, attr::MOI.ConstraintName, ci::CI{F, S})
 end
 
 MOI.get(uf::UniversalFallback, ::Type{VI}, name::String) = MOI.get(uf.model, VI, name)
+
+check_type_and_multiple_names(::Type, ::Nothing, ::Nothing, name) = nothing
+check_type_and_multiple_names(::Type{T}, value::T, ::Nothing, name) where T = value
+check_type_and_multiple_names(::Type, ::Any, ::Nothing, name) where T = nothing
+check_type_and_multiple_names(::Type{T}, ::Nothing, value::T, name) where T = value
+check_type_and_multiple_names(::Type, ::Nothing, ::Any, name) where T = nothing
+function check_type_and_multiple_names(T::Type, ::Any, ::Any, name)
+    throw_multiple_name_error(T, name)
+end
 function MOI.get(uf::UniversalFallback, ::Type{CI{F, S}}, name::String) where {F, S}
     if uf.name_to_con === nothing
         uf.name_to_con = build_name_to_con_map(uf.con_to_name)
     end
-
     if MOI.supports_constraint(uf.model, F, S)
         ci = MOI.get(uf.model, CI{F, S}, name)
-        if ci !== nothing && haskey(uf.name_to_con, name)
-            error("Multiple constraints have the name $name.")
-        end
-        return ci
     else
-        ci = get(uf.name_to_con, name, nothing)
-        if ci == CI{Nothing, Nothing}(-1)
-            error("Multiple constraints have the name $name.")
-        elseif ci isa CI{F, S}
-            return ci
-        else
-            return nothing
-        end
+        # There is no `F`-in-`S` constraint in `b.model`, `ci` is only got
+        # to check for duplicate names.
+        ci = MOI.get(uf.model, CI, name)
     end
+    ci_uf = get(uf.name_to_con, name, nothing)
+    throw_if_multiple_with_name(ci_uf, name)
+    return check_type_and_multiple_names(CI{F, S}, ci_uf, ci, name)
 end
 function MOI.get(uf::UniversalFallback, ::Type{CI}, name::String)
     if uf.name_to_con === nothing
         uf.name_to_con = build_name_to_con_map(uf.con_to_name)
     end
-
-    ci = MOI.get(uf.model, CI, name)
-    if ci === nothing
-        uf_ci = get(uf.name_to_con, name, nothing)
-        if uf_ci == CI{Nothing, Nothing}(-1)
-            error("Multiple constraints have the name $name.")
-        else
-            return uf_ci
-        end
-    else
-        if haskey(uf.name_to_con, name)
-            error("Multiple constraints have the name $name.")
-        end
-        return ci
-    end
+    ci_uf = get(uf.name_to_con, name, nothing)
+    throw_if_multiple_with_name(ci_uf, name)
+    return check_type_and_multiple_names(
+        CI, ci_uf, MOI.get(uf.model, CI, name), name)
 end
 
 _set(uf, attr::MOI.AbstractOptimizerAttribute, value) = uf.optattr[attr] = value
diff --git a/test/Utilities/model.jl b/test/Utilities/model.jl
index b27e0dedeb..793cb8e8d2 100644
--- a/test/Utilities/model.jl
+++ b/test/Utilities/model.jl
@@ -130,6 +130,10 @@ end
     c7 = MOI.add_constraint(model, f7, MOI.Nonpositives(2))
     @test 1 == @inferred MOI.get(model, MOI.NumberOfConstraints{MOI.VectorOfVariables,MOI.Nonpositives}())
 
+    f8 = MOI.VectorOfVariables([x, y])
+    c8 = MOI.add_constraint(model, f8, MOI.SecondOrderCone(2))
+    @test 1 == @inferred MOI.get(model, MOI.NumberOfConstraints{MOI.VectorOfVariables,MOI.SecondOrderCone}())
+
     loc1 = MOI.get(model, MOI.ListOfConstraints())
     loc2 = Vector{Tuple{DataType, DataType}}()
     function _pushloc(constrs::Vector{MOIU.ConstraintEntry{F, S}}) where {F, S}
@@ -139,7 +143,7 @@ end
     end
     MOIU.broadcastcall(_pushloc, model)
     for loc in (loc1, loc2)
-        @test length(loc) == 5
+        @test length(loc) == 6
         @test (MOI.VectorQuadraticFunction{Int},MOI.PositiveSemidefiniteConeTriangle) in loc
         @test (MOI.VectorQuadraticFunction{Int},MOI.PositiveSemidefiniteConeTriangle) in loc
         @test (MOI.VectorOfVariables,MOI.RotatedSecondOrderCone) in loc
@@ -154,6 +158,16 @@ end
     @test 1 == @inferred MOI.get(model, MOI.NumberOfConstraints{MOI.VectorAffineFunction{Int},MOI.SecondOrderCone}())
     @test MOI.get(model, MOI.ConstraintFunction(), c6).constants == f6.constants
 
+    message = string("Cannot delete variable as it is constrained with other",
+                     " other variables in a `MOI.VectorOfVariables`.")
+    err = MOI.DeleteNotAllowed(y, message)
+    @test_throws err MOI.delete(model, y)
+
+    @test MOI.is_valid(model, c8)
+    MOI.delete(model, c8)
+    @test !MOI.is_valid(model, c8)
+    @test 0 == @inferred MOI.get(model, MOI.NumberOfConstraints{MOI.VectorOfVariables,MOI.SecondOrderCone}())
+
     MOI.delete(model, y)
 
     f = MOI.get(model, MOI.ConstraintFunction(), c2)
@@ -165,12 +179,14 @@ end
     @test f.terms == MOI.VectorAffineTerm.([1], MOI.ScalarAffineTerm.([2], [x]))
     @test f.constants == [6, 8]
 
+    @test 1 == @inferred MOI.get(model, MOI.NumberOfConstraints{MOI.VectorOfVariables,MOI.Nonpositives}())
+    @test [c7] == @inferred MOI.get(model, MOI.ListOfConstraintIndices{MOI.VectorOfVariables,MOI.Nonpositives}())
+
     f =  MOI.get(model, MOI.ConstraintFunction(), c7)
     @test f.variables == [x]
 
     s =  MOI.get(model, MOI.ConstraintSet(), c7)
     @test MOI.dimension(s) == 1
-
 end
 
 # We create a new function and set to test catching errors if users create their
diff --git a/test/Utilities/universalfallback.jl b/test/Utilities/universalfallback.jl
index 47283486e7..5219f3c30c 100644
--- a/test/Utilities/universalfallback.jl
+++ b/test/Utilities/universalfallback.jl
@@ -204,3 +204,63 @@ end
                                    "a name")
     @test_throws Exception MOI.get(uf, MOI.ConstraintIndex, "a name")
 end
+
+@testset "Delete" begin
+    model = ModelForUniversalFallback{Float64}()
+    uf = MOIU.UniversalFallback(model)
+    x, cx = MOI.add_constrained_variable(uf, MOI.GreaterThan(0.0))
+    y, cy = MOI.add_constrained_variables(uf, MOI.Nonpositives(4))
+    @test MOI.is_valid(uf, x)
+    @test MOI.is_valid(uf, y[1])
+    @test MOI.is_valid(uf, y[2])
+    @test MOI.is_valid(uf, y[3])
+    @test MOI.is_valid(uf, y[4])
+    @test MOI.is_valid(uf, cx)
+    @test MOI.is_valid(uf, cy)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
+    @test MOI.get(uf, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y)
+    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(4)
+    MOI.delete(uf, y[3])
+    @test MOI.is_valid(uf, x)
+    @test MOI.is_valid(uf, y[1])
+    @test MOI.is_valid(uf, y[2])
+    @test !MOI.is_valid(uf, y[3])
+    @test MOI.is_valid(uf, y[4])
+    @test MOI.is_valid(uf, cx)
+    @test MOI.is_valid(uf, cy)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
+    @test MOI.get(uf, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[1, 2, 4]])
+    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(3)
+    MOI.delete(uf, y[1])
+    @test MOI.is_valid(uf, x)
+    @test !MOI.is_valid(uf, y[1])
+    @test MOI.is_valid(uf, y[2])
+    @test !MOI.is_valid(uf, y[3])
+    @test MOI.is_valid(uf, y[4])
+    @test MOI.is_valid(uf, cx)
+    @test MOI.is_valid(uf, cy)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
+    @test MOI.get(uf, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
+    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
+    MOI.delete(uf, x)
+    @test !MOI.is_valid(uf, x)
+    @test !MOI.is_valid(uf, y[1])
+    @test MOI.is_valid(uf, y[2])
+    @test !MOI.is_valid(uf, y[3])
+    @test MOI.is_valid(uf, y[4])
+    @test !MOI.is_valid(uf, cx)
+    @test MOI.is_valid(uf, cy)
+    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
+    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
+    MOI.delete(uf, y[[2, 4]])
+    @test !MOI.is_valid(uf, x)
+    @test !MOI.is_valid(uf, y[1])
+    @test !MOI.is_valid(uf, y[2])
+    @test !MOI.is_valid(uf, y[3])
+    @test !MOI.is_valid(uf, y[4])
+    @test !MOI.is_valid(uf, cx)
+    @test !MOI.is_valid(uf, cy)
+end

From 29a1938ba4fcbc32480d7f870c72da86c052fe63 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 16:28:10 +0200
Subject: [PATCH 02/12] Add standalone test

---
 src/Test/modellike.jl               | 60 +++++++++++++++++++++++++++++
 test/Utilities/mockoptimizer.jl     |  5 +++
 test/Utilities/model.jl             |  4 ++
 test/Utilities/universalfallback.jl | 56 +--------------------------
 4 files changed, 70 insertions(+), 55 deletions(-)

diff --git a/src/Test/modellike.jl b/src/Test/modellike.jl
index 88494d0057..c54b5947b3 100644
--- a/src/Test/modellike.jl
+++ b/src/Test/modellike.jl
@@ -471,3 +471,63 @@ function set_upper_bound_twice(model::MOI.ModelLike, T::Type)
         MOI.delete(model, ci)
     end
 end
+
+function delete_test(model::MOI.ModelLike)
+    x = MOI.add_variable(model)
+    cx = MOI.add_constraint(model, x, MOI.GreaterThan(0.0))
+    y = MOI.add_variables(model, 4)
+    cy = MOI.add_constraint(model, y, MOI.Nonpositives(4))
+    @test MOI.is_valid(model, x)
+    @test MOI.is_valid(model, y[1])
+    @test MOI.is_valid(model, y[2])
+    @test MOI.is_valid(model, y[3])
+    @test MOI.is_valid(model, y[4])
+    @test MOI.is_valid(model, cx)
+    @test MOI.is_valid(model, cy)
+    @test MOI.get(model, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
+    @test MOI.get(model, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
+    @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y)
+    @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(4)
+    MOI.delete(model, y[3])
+    @test MOI.is_valid(model, x)
+    @test MOI.is_valid(model, y[1])
+    @test MOI.is_valid(model, y[2])
+    @test !MOI.is_valid(model, y[3])
+    @test MOI.is_valid(model, y[4])
+    @test MOI.is_valid(model, cx)
+    @test MOI.is_valid(model, cy)
+    @test MOI.get(model, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
+    @test MOI.get(model, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
+    @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[1, 2, 4]])
+    @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(3)
+    MOI.delete(model, y[1])
+    @test MOI.is_valid(model, x)
+    @test !MOI.is_valid(model, y[1])
+    @test MOI.is_valid(model, y[2])
+    @test !MOI.is_valid(model, y[3])
+    @test MOI.is_valid(model, y[4])
+    @test MOI.is_valid(model, cx)
+    @test MOI.is_valid(model, cy)
+    @test MOI.get(model, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
+    @test MOI.get(model, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
+    @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
+    @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
+    MOI.delete(model, x)
+    @test !MOI.is_valid(model, x)
+    @test !MOI.is_valid(model, y[1])
+    @test MOI.is_valid(model, y[2])
+    @test !MOI.is_valid(model, y[3])
+    @test MOI.is_valid(model, y[4])
+    @test !MOI.is_valid(model, cx)
+    @test MOI.is_valid(model, cy)
+    @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
+    @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
+    MOI.delete(model, y[[2, 4]])
+    @test !MOI.is_valid(model, x)
+    @test !MOI.is_valid(model, y[1])
+    @test !MOI.is_valid(model, y[2])
+    @test !MOI.is_valid(model, y[3])
+    @test !MOI.is_valid(model, y[4])
+    @test !MOI.is_valid(model, cx)
+    @test !MOI.is_valid(model, cy)
+end
diff --git a/test/Utilities/mockoptimizer.jl b/test/Utilities/mockoptimizer.jl
index ef9f6b78d2..204deef88f 100644
--- a/test/Utilities/mockoptimizer.jl
+++ b/test/Utilities/mockoptimizer.jl
@@ -90,3 +90,8 @@ end
     @test MOI.get(optimizer, MOI.ConstraintDual(), c1) == 5.9
     @test MOI.get(optimizer, MOI.ConstraintDual(), soc) == [1.0,2.0]
 end
+
+@testset "Delete" begin
+    mock = MOIU.MockOptimizer(MOIU.Model{Float64}())
+    MOIT.delete_test(mock)
+end
diff --git a/test/Utilities/model.jl b/test/Utilities/model.jl
index 793cb8e8d2..a9f8f2a28f 100644
--- a/test/Utilities/model.jl
+++ b/test/Utilities/model.jl
@@ -59,6 +59,10 @@ end
     MOIT.validtest(MOIU.Model{Float64}())
 end
 
+@testset "Delete test" begin
+    MOIT.delete_test(MOIU.Model{Float64}())
+end
+
 @testset "Empty test" begin
     MOIT.emptytest(MOIU.Model{Float64}())
 end
diff --git a/test/Utilities/universalfallback.jl b/test/Utilities/universalfallback.jl
index 5219f3c30c..2bf41a9640 100644
--- a/test/Utilities/universalfallback.jl
+++ b/test/Utilities/universalfallback.jl
@@ -208,59 +208,5 @@ end
 @testset "Delete" begin
     model = ModelForUniversalFallback{Float64}()
     uf = MOIU.UniversalFallback(model)
-    x, cx = MOI.add_constrained_variable(uf, MOI.GreaterThan(0.0))
-    y, cy = MOI.add_constrained_variables(uf, MOI.Nonpositives(4))
-    @test MOI.is_valid(uf, x)
-    @test MOI.is_valid(uf, y[1])
-    @test MOI.is_valid(uf, y[2])
-    @test MOI.is_valid(uf, y[3])
-    @test MOI.is_valid(uf, y[4])
-    @test MOI.is_valid(uf, cx)
-    @test MOI.is_valid(uf, cy)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
-    @test MOI.get(uf, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y)
-    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(4)
-    MOI.delete(uf, y[3])
-    @test MOI.is_valid(uf, x)
-    @test MOI.is_valid(uf, y[1])
-    @test MOI.is_valid(uf, y[2])
-    @test !MOI.is_valid(uf, y[3])
-    @test MOI.is_valid(uf, y[4])
-    @test MOI.is_valid(uf, cx)
-    @test MOI.is_valid(uf, cy)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
-    @test MOI.get(uf, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[1, 2, 4]])
-    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(3)
-    MOI.delete(uf, y[1])
-    @test MOI.is_valid(uf, x)
-    @test !MOI.is_valid(uf, y[1])
-    @test MOI.is_valid(uf, y[2])
-    @test !MOI.is_valid(uf, y[3])
-    @test MOI.is_valid(uf, y[4])
-    @test MOI.is_valid(uf, cx)
-    @test MOI.is_valid(uf, cy)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cx) == MOI.SingleVariable(x)
-    @test MOI.get(uf, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
-    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
-    MOI.delete(uf, x)
-    @test !MOI.is_valid(uf, x)
-    @test !MOI.is_valid(uf, y[1])
-    @test MOI.is_valid(uf, y[2])
-    @test !MOI.is_valid(uf, y[3])
-    @test MOI.is_valid(uf, y[4])
-    @test !MOI.is_valid(uf, cx)
-    @test MOI.is_valid(uf, cy)
-    @test MOI.get(uf, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
-    @test MOI.get(uf, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
-    MOI.delete(uf, y[[2, 4]])
-    @test !MOI.is_valid(uf, x)
-    @test !MOI.is_valid(uf, y[1])
-    @test !MOI.is_valid(uf, y[2])
-    @test !MOI.is_valid(uf, y[3])
-    @test !MOI.is_valid(uf, y[4])
-    @test !MOI.is_valid(uf, cx)
-    @test !MOI.is_valid(uf, cy)
+    MOIT.delete_test(uf)
 end

From e7f21c3e31e38072b6282f0493f8d6a6f9e52f05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 16:55:00 +0200
Subject: [PATCH 03/12] Update remove_variable call

---
 src/Bridges/Constraint/slack.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Bridges/Constraint/slack.jl b/src/Bridges/Constraint/slack.jl
index 0d681aaa72..4b887ca1b7 100644
--- a/src/Bridges/Constraint/slack.jl
+++ b/src/Bridges/Constraint/slack.jl
@@ -93,7 +93,7 @@ end
 
 function MOI.get(model::MOI.ModelLike, attr::MOI.ConstraintFunction,
                  b::ScalarSlackBridge{T}) where T
-    return MOIU.removevariable(MOI.get(model, attr, b.equality), b.slack)
+    return MOIU.remove_variable(MOI.get(model, attr, b.equality), b.slack)
 end
 function MOI.get(model::MOI.ModelLike, attr::MOI.ConstraintSet,
                  b::ScalarSlackBridge)
@@ -191,7 +191,7 @@ end
 
 function MOI.get(model::MOI.ModelLike, attr::MOI.ConstraintFunction,
                  b::VectorSlackBridge{T}) where T
-    return MOIU.removevariable(MOI.get(model, attr, b.equality), b.slacks)
+    return MOIU.remove_variable(MOI.get(model, attr, b.equality), b.slacks)
 end
 function MOI.get(model::MOI.ModelLike, attr::MOI.ConstraintSet,
                  b::VectorSlackBridge)

From 859061ef83dcc57b46ad0c125b228ced4e921261 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 16:55:08 +0200
Subject: [PATCH 04/12] Update doc

---
 docs/src/apireference.md | 37 +++++++++++++++++++++++++++++++++++++
 src/Utilities/sets.jl    | 34 ++++++++++++++++++++++++++--------
 src/indextypes.jl        | 18 +++++++++++++++++-
 3 files changed, 80 insertions(+), 9 deletions(-)

diff --git a/docs/src/apireference.md b/docs/src/apireference.md
index 2bdb4f5b46..e08822ef04 100644
--- a/docs/src/apireference.md
+++ b/docs/src/apireference.md
@@ -612,6 +612,43 @@ Utilities.state
 Utilities.mode
 ```
 
+## Function utilities
+
+The following utilities are available for functions:
+```@docs
+Utilities.evalvariables
+Utilities.remove_variable
+Utilities.all_coefficients
+Utilities.unsafe_add
+Utilities.isapprox_zero
+Utilities.modifyfunction
+```
+
+The following functions can be used to canonicalize a function:
+```@docs
+Utilities.iscanonical
+Utilities.canonical
+Utilities.canonicalize!
+```
+
+The following functions can be used to manipulate functions with basic algebra:
+```@docs
+Utilities.scalar_type
+Utilities.promote_operation
+Utilities.operate
+Utilities.operate!
+Utilities.vectorize
+```
+
+## Set utilities
+
+The following utilities are available for sets:
+```@docs
+Utilities.supports_dimension_update
+Utilities.update_dimension
+Utilities.shift_constant
+```
+
 ## Benchmarks
 
 Functions to help benchmark the performance of solver wrappers. See
diff --git a/src/Utilities/sets.jl b/src/Utilities/sets.jl
index 4a5cc367e2..c5684b2eca 100644
--- a/src/Utilities/sets.jl
+++ b/src/Utilities/sets.jl
@@ -1,14 +1,32 @@
-const DimensionUpdatableSets = Union{MOI.Reals,
-                                     MOI.Zeros,
-                                     MOI.Nonnegatives,
-                                     MOI.Nonpositives}
 """
-    update_dimension(s::AbstractVectorSet, newdim)
+    supports_dimension_update(S::Type{<:MOI.AbstractVectorSet})
 
-Returns a set with the dimension modified to `newdim`.
+Return a `Bool` indicating whether the elimination of any dimension of
+`n`-dimensional sets of type `S` give an `n-1`-dimensional set `S`.
+By default, this function returns `false` so it should only be implemented
+for sets that supports dimension update.
+
+For instance, `supports_dimension_update(MOI.Nonnegatives}` is `true` because
+the elimination of any dimension of the `n`-dimensional nonnegative orthant
+gives the `n-1`-dimensional nonnegative orthant. However
+`supports_dimension_update(MOI.ExponentialCone}` is `false`.
+"""
+function supports_dimension_update(::Type{<:MOI.AbstractVectorSet})
+    return false
+end
+function supports_dimension_update(::Union{
+    MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives})
+    return true
+end
+
+"""
+    update_dimension(s::AbstractVectorSet, new_dim)
+
+Returns a set with the dimension modified to `new_dim`.
 """
-function update_dimension(::S, newdim) where S<:DimensionUpdatableSets
-    S(newdim)
+function update_dimension(S::Union{
+    MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives}, new_dim)
+    return S(new_dim)
 end
 
 """
diff --git a/src/indextypes.jl b/src/indextypes.jl
index 8954a64506..0a4560e909 100644
--- a/src/indextypes.jl
+++ b/src/indextypes.jl
@@ -95,7 +95,23 @@ end
 """
     delete(model::ModelLike, index::Index)
 
-Delete the referenced object from the model.
+Delete the referenced object from the model. Throw [`DeleteNotAllowed`](@ref) if
+if `index` cannot be deleted.
+
+The following modifications also take effect if `Index` is [`VariableIndex`](@ref):
+* If `index` used in the objective function, it is removed from the function;
+  see [`Utilities.remove_variable`](@ref).
+* For each `func`-in-`set` constraint of the model:
+  - If `func isa SingleVariable` and `func.variable == index` then the
+    constraint is deleted.
+  - If `func isa VectorOfVariables` and `index in func.variable` then
+    * if `length(func.variable) == 1` is one, the constraint is deleted;
+    * if `length(func.variable) > 1` and `supports_dimension_update(set)` then
+      then the variable is removed from `func` and `set` is replaced by
+      `update_dimension(set, MOI.dimension(set) - 1)`.
+    * Otherwise, a [`DeleteNotAllowed`](@ref) error is thrown.
+  - Otherwise, the variable is removed from `func`; see
+    [`Utilities.remove_variable`](@ref).
 """
 delete(model::ModelLike, index::Index) = throw(DeleteNotAllowed(index))
 

From 689db299da48378693c09a797ea69c030bc203db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 17:36:06 -0400
Subject: [PATCH 05/12] Fixes

---
 src/Utilities/model.jl             | 10 +++++-----
 src/Utilities/sets.jl              |  8 ++++----
 src/Utilities/universalfallback.jl |  2 +-
 test/Utilities/model.jl            |  2 +-
 4 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/Utilities/model.jl b/src/Utilities/model.jl
index 402d6402d3..5fb31004cc 100644
--- a/src/Utilities/model.jl
+++ b/src/Utilities/model.jl
@@ -133,7 +133,7 @@ function _vector_of_variables_with(::Vector, ::Union{VI, MOI.Vector{VI}})
 end
 function throw_delete_variable_in_vov(vi::VI)
     message = string("Cannot delete variable as it is constrained with other",
-                     " other variables in a `MOI.VectorOfVariables`.")
+                     " variables in a `MOI.VectorOfVariables`.")
     throw(MOI.DeleteNotAllowed(vi, message))
 end
 function _vector_of_variables_with(
@@ -142,9 +142,9 @@ function _vector_of_variables_with(
     for (ci, f, s) in constrs
         if vi in f.variables
             if length(f.variables) > 1
-                # If `s isa DimensionUpdatableSets` then the variable will be
+                # If `supports_dimension_update(s)` then the variable will be
                 # removed in `_remove_variable`.
-                if !(s isa DimensionUpdatableSets)
+                if !supports_dimension_update(typeof(s))
                     throw_delete_variable_in_vov(vi)
                 end
             else
@@ -176,8 +176,8 @@ function MOI.delete(model::AbstractModel{T}, vi::VI) where T
     for ci in vov_to_remove
         MOI.delete(model, ci)
     end
-    # `VectorOfVariables` constraints with non-`DimensionUpdatableSets` were
-    # either deleted or an error was thrown. The rest is modified now.
+    # `VectorOfVariables` constraints with sets not supporting dimension update
+    # were either deleted or an error was thrown. The rest is modified now.
     broadcastcall(constrs -> _remove_variable(constrs, vi), model)
     model.single_variable_mask[vi.value] = 0x0
     if model.variable_indices === nothing
diff --git a/src/Utilities/sets.jl b/src/Utilities/sets.jl
index c5684b2eca..aa6e178def 100644
--- a/src/Utilities/sets.jl
+++ b/src/Utilities/sets.jl
@@ -14,8 +14,8 @@ gives the `n-1`-dimensional nonnegative orthant. However
 function supports_dimension_update(::Type{<:MOI.AbstractVectorSet})
     return false
 end
-function supports_dimension_update(::Union{
-    MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives})
+function supports_dimension_update(::Type{<:Union{
+    MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives}})
     return true
 end
 
@@ -24,9 +24,9 @@ end
 
 Returns a set with the dimension modified to `new_dim`.
 """
-function update_dimension(S::Union{
+function update_dimension(set::Union{
     MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives}, new_dim)
-    return S(new_dim)
+    return typeof(set)(new_dim)
 end
 
 """
diff --git a/src/Utilities/universalfallback.jl b/src/Utilities/universalfallback.jl
index c9550bc71f..4338fc1c6d 100644
--- a/src/Utilities/universalfallback.jl
+++ b/src/Utilities/universalfallback.jl
@@ -99,7 +99,7 @@ function _remove_variable(uf::UniversalFallback,
         f::MOI.VectorOfVariables, s = constraint
         if vi in f.variables
             if length(f.variables) > 1
-                if S <: MOIU.DimensionUpdatableSets
+                if supports_dimension_update(S)
                     constraints[ci] = remove_variable(f, s, vi)
                 else
                     throw_delete_variable_in_vov(vi)
diff --git a/test/Utilities/model.jl b/test/Utilities/model.jl
index a9f8f2a28f..78010f9a05 100644
--- a/test/Utilities/model.jl
+++ b/test/Utilities/model.jl
@@ -163,7 +163,7 @@ end
     @test MOI.get(model, MOI.ConstraintFunction(), c6).constants == f6.constants
 
     message = string("Cannot delete variable as it is constrained with other",
-                     " other variables in a `MOI.VectorOfVariables`.")
+                     " variables in a `MOI.VectorOfVariables`.")
     err = MOI.DeleteNotAllowed(y, message)
     @test_throws err MOI.delete(model, y)
 

From d2f3f260965e0adfa03f4ea2ea74b427dd7e47d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 18:20:01 -0400
Subject: [PATCH 06/12] Rename evalvariables and modifyobjective

---
 docs/src/apireference.md           |  2 +-
 src/Utilities/functions.jl         | 34 ++++++++++----------
 src/Utilities/model.jl             |  4 +--
 src/Utilities/results.jl           |  4 +--
 src/Utilities/universalfallback.jl |  2 +-
 test/Utilities/functions.jl        | 50 +++++++++++++++---------------
 test/Utilities/model.jl            |  4 +--
 7 files changed, 50 insertions(+), 50 deletions(-)

diff --git a/docs/src/apireference.md b/docs/src/apireference.md
index e08822ef04..6193ef7be1 100644
--- a/docs/src/apireference.md
+++ b/docs/src/apireference.md
@@ -616,7 +616,7 @@ Utilities.mode
 
 The following utilities are available for functions:
 ```@docs
-Utilities.evalvariables
+Utilities.eval_variables
 Utilities.remove_variable
 Utilities.all_coefficients
 Utilities.unsafe_add
diff --git a/src/Utilities/functions.jl b/src/Utilities/functions.jl
index d46fc18ad1..04b0c50ca6 100644
--- a/src/Utilities/functions.jl
+++ b/src/Utilities/functions.jl
@@ -1,30 +1,30 @@
 using Test
 
 """
-    evalvariables(varval::Function, f::AbstractFunction)
+    eval_variables(varval::Function, f::AbstractFunction)
 
 Returns the value of function `f` if each variable index `vi` is evaluated as `varval(vi)`.
 """
-function evalvariables end
-evalvariables(varval::Function, f::SVF) = varval(f.variable)
-evalvariables(varval::Function, f::VVF) = varval.(f.variables)
-function evalvariables(varval::Function, f::SAF)
+function eval_variables end
+eval_variables(varval::Function, f::SVF) = varval(f.variable)
+eval_variables(varval::Function, f::VVF) = varval.(f.variables)
+function eval_variables(varval::Function, f::SAF)
     return mapreduce(t->evalterm(varval, t), +, f.terms, init=f.constant)
 end
-function evalvariables(varval::Function, f::VAF)
+function eval_variables(varval::Function, f::VAF)
     out = copy(f.constants)
     for t in f.terms
         out[t.output_index] += evalterm(varval, t.scalar_term)
     end
     out
 end
-function evalvariables(varval::Function, f::SQF)
+function eval_variables(varval::Function, f::SQF)
     init = zero(f.constant)
     lin = mapreduce(t->evalterm(varval, t), +, f.affine_terms, init=init)
     quad = mapreduce(t->evalterm(varval, t), +, f.quadratic_terms, init=init)
     return lin + quad + f.constant
 end
-function evalvariables(varval::Function, f::VQF)
+function eval_variables(varval::Function, f::VQF)
     out = copy(f.constants)
     for t in f.affine_terms
         out[t.output_index] += evalterm(varval, t.scalar_term)
@@ -484,20 +484,20 @@ function remove_variable(f::Union{SQF, VQF}, vi)
 end
 
 """
-    modifyfunction(f::AbstractFunction, change::AbstractFunctionModification)
+    modify_function(f::AbstractFunction, change::AbstractFunctionModification)
 
 Return a new function `f` modified according to `change`.
 """
-function modifyfunction(f::SAF, change::MOI.ScalarConstantChange)
+function modify_function(f::SAF, change::MOI.ScalarConstantChange)
     return SAF(f.terms, change.new_constant)
 end
-function modifyfunction(f::VAF, change::MOI.VectorConstantChange)
+function modify_function(f::VAF, change::MOI.VectorConstantChange)
     return VAF(f.terms, change.new_constant)
 end
-function modifyfunction(f::SQF, change::MOI.ScalarConstantChange)
+function modify_function(f::SQF, change::MOI.ScalarConstantChange)
     return SQF(f.affine_terms, f.quadratic_terms, change.new_constant)
 end
-function modifyfunction(f::VQF, change::MOI.VectorConstantChange)
+function modify_function(f::VQF, change::MOI.VectorConstantChange)
     return VQF(f.affine_terms, f.quadratic_terms, change.new_constant)
 end
 function _modifycoefficient(terms::Vector{<:MOI.ScalarAffineTerm}, variable::VI, new_coefficient)
@@ -518,11 +518,11 @@ function _modifycoefficient(terms::Vector{<:MOI.ScalarAffineTerm}, variable::VI,
     end
     terms
 end
-function modifyfunction(f::SAF, change::MOI.ScalarCoefficientChange)
+function modify_function(f::SAF, change::MOI.ScalarCoefficientChange)
     lin = _modifycoefficient(f.terms, change.variable, change.new_coefficient)
     return SAF(lin, f.constant)
 end
-function modifyfunction(f::SQF, change::MOI.ScalarCoefficientChange)
+function modify_function(f::SQF, change::MOI.ScalarCoefficientChange)
     lin = _modifycoefficient(f.affine_terms, change.variable, change.new_coefficient)
     return SQF(lin, f.quadratic_terms, f.constant)
 end
@@ -553,13 +553,13 @@ function _modifycoefficients(n, terms::Vector{<:MOI.VectorAffineTerm}, variable:
     end
     terms
 end
-function modifyfunction(f::VAF, change::MOI.MultirowChange)
+function modify_function(f::VAF, change::MOI.MultirowChange)
     dim = MOI.output_dimension(f)
     coefficients = change.new_coefficients
     lin = _modifycoefficients(dim, f.terms, change.variable, coefficients)
     VAF(lin, f.constants)
 end
-function modifyfunction(f::VQF, change::MOI.MultirowChange)
+function modify_function(f::VQF, change::MOI.MultirowChange)
     dim = MOI.output_dimension(f)
     coefficients = change.new_coefficients
     lin = _modifycoefficients(dim, f.affine_terms, change.variable, coefficients)
diff --git a/src/Utilities/model.jl b/src/Utilities/model.jl
index 5fb31004cc..47ff2803b1 100644
--- a/src/Utilities/model.jl
+++ b/src/Utilities/model.jl
@@ -49,7 +49,7 @@ end
 
 _modifyconstr(ci::CI{F, S}, f::F, s::S, change::F) where {F, S} = (ci, change, s)
 _modifyconstr(ci::CI{F, S}, f::F, s::S, change::S) where {F, S} = (ci, f, change)
-_modifyconstr(ci::CI{F, S}, f::F, s::S, change::MOI.AbstractFunctionModification) where {F, S} = (ci, modifyfunction(f, change), s)
+_modifyconstr(ci::CI{F, S}, f::F, s::S, change::MOI.AbstractFunctionModification) where {F, S} = (ci, modify_function(f, change), s)
 function _modify(constrs::Vector{ConstraintEntry{F, S}}, ci::CI{F}, i::Int,
                  change) where {F, S}
     constrs[i] = _modifyconstr(constrs[i]..., change)
@@ -373,7 +373,7 @@ function MOI.set(model::AbstractModel, ::MOI.ObjectiveFunction, f::MOI.AbstractF
 end
 
 function MOI.modify(model::AbstractModel, obj::MOI.ObjectiveFunction, change::MOI.AbstractFunctionModification)
-    model.objective = modifyfunction(model.objective, change)
+    model.objective = modify_function(model.objective, change)
 end
 
 MOI.get(::AbstractModel, ::MOI.ListOfOptimizerAttributesSet) = MOI.AbstractOptimizerAttribute[]
diff --git a/src/Utilities/results.jl b/src/Utilities/results.jl
index a6662305bc..2d17de6734 100644
--- a/src/Utilities/results.jl
+++ b/src/Utilities/results.jl
@@ -20,7 +20,7 @@ function get_fallback(model::MOI.ModelLike, ::MOI.ObjectiveValue)
     F = MOI.get(model, MOI.ObjectiveFunctionType())
     f = MOI.get(model, MOI.ObjectiveFunction{F}())
     # TODO do not include constant if primal solution is a ray
-    return evalvariables(vi -> MOI.get(model, MOI.VariablePrimal(), vi), f)
+    return eval_variables(vi -> MOI.get(model, MOI.VariablePrimal(), vi), f)
 end
 
 function constraint_constant(model::MOI.ModelLike,
@@ -149,7 +149,7 @@ function get_fallback(model::MOI.ModelLike, ::MOI.ConstraintPrimal,
                       idx::MOI.ConstraintIndex)
     f = MOI.get(model, MOI.ConstraintFunction(), idx)
     # TODO do not include constant if primal solution is a ray
-    return evalvariables(vi -> MOI.get(model, MOI.VariablePrimal(), vi), f)
+    return eval_variables(vi -> MOI.get(model, MOI.VariablePrimal(), vi), f)
 end
 
 ################ Constraint Dual for Variable-wise constraints #################
diff --git a/src/Utilities/universalfallback.jl b/src/Utilities/universalfallback.jl
index 4338fc1c6d..e135186ddc 100644
--- a/src/Utilities/universalfallback.jl
+++ b/src/Utilities/universalfallback.jl
@@ -370,7 +370,7 @@ function MOI.modify(uf::UniversalFallback, ci::CI{F, S}, change::MOI.AbstractFun
         MOI.modify(uf.model, ci, change)
     else
         (f, s) = uf.constraints[(F, S)][ci]
-        uf.constraints[(F, S)][ci] = (modifyfunction(f, change), s)
+        uf.constraints[(F, S)][ci] = (modify_function(f, change), s)
     end
 end
 
diff --git a/test/Utilities/functions.jl b/test/Utilities/functions.jl
index b83e3040f0..116c720efe 100644
--- a/test/Utilities/functions.jl
+++ b/test/Utilities/functions.jl
@@ -75,35 +75,35 @@ end
     @test MOI.VectorQuadraticTerm(Int32(3), scalarquad) === MOI.VectorQuadraticTerm(Int64(3), scalarquad)
     @test MOI.VectorQuadraticTerm{Float64}(Int32(3), scalarquad) === MOI.VectorQuadraticTerm(Int64(3), scalarquad)
 end
-@testset "evalvariables" begin
+@testset "eval_variables" begin
     # We do tests twice to make sure the function is not modified
     vals = Dict(w=>0, x=>3, y=>1, z=>5)
     fsv = MOI.SingleVariable(z)
     @test MOI.output_dimension(fsv) == 1
-    @test MOIU.evalvariables(vi -> vals[vi], fsv) ≈ 5
-    @test MOIU.evalvariables(vi -> vals[vi], fsv) ≈ 5
+    @test MOIU.eval_variables(vi -> vals[vi], fsv) ≈ 5
+    @test MOIU.eval_variables(vi -> vals[vi], fsv) ≈ 5
     fvv = MOI.VectorOfVariables([x, z, y])
     @test MOI.output_dimension(fvv) == 3
-    @test MOIU.evalvariables(vi -> vals[vi], fvv) ≈ [3, 5, 1]
-    @test MOIU.evalvariables(vi -> vals[vi], fvv) ≈ [3, 5, 1]
+    @test MOIU.eval_variables(vi -> vals[vi], fvv) ≈ [3, 5, 1]
+    @test MOIU.eval_variables(vi -> vals[vi], fvv) ≈ [3, 5, 1]
     fsa = MOI.ScalarAffineFunction([MOI.ScalarAffineTerm(1.0, x), MOI.ScalarAffineTerm(3.0, z), MOI.ScalarAffineTerm(2.0, y)], 2.0)
     @test MOI.output_dimension(fsa) == 1
-    @test MOIU.evalvariables(vi -> vals[vi], fsa) ≈ 22
-    @test MOIU.evalvariables(vi -> vals[vi], fsa) ≈ 22
+    @test MOIU.eval_variables(vi -> vals[vi], fsa) ≈ 22
+    @test MOIU.eval_variables(vi -> vals[vi], fsa) ≈ 22
     fva = MOI.VectorAffineFunction(MOI.VectorAffineTerm.([2, 1, 2], MOI.ScalarAffineTerm.([1.0, 3.0, 2.0], [x, z, y])), [-3.0, 2.0])
     @test MOI.output_dimension(fva) == 2
-    @test MOIU.evalvariables(vi -> vals[vi], fva) ≈ [12, 7]
-    @test MOIU.evalvariables(vi -> vals[vi], fva) ≈ [12, 7]
+    @test MOIU.eval_variables(vi -> vals[vi], fva) ≈ [12, 7]
+    @test MOIU.eval_variables(vi -> vals[vi], fva) ≈ [12, 7]
     fsq = MOI.ScalarQuadraticFunction(MOI.ScalarAffineTerm.(1.0, [x, y]),
                                       MOI.ScalarQuadraticTerm.(1.0, [x, w, w], [z, z, y]), -3.0)
     @test MOI.output_dimension(fsq) == 1
-    @test MOIU.evalvariables(vi -> vals[vi], fsq) ≈ 16
-    @test MOIU.evalvariables(vi -> vals[vi], fsq) ≈ 16
+    @test MOIU.eval_variables(vi -> vals[vi], fsq) ≈ 16
+    @test MOIU.eval_variables(vi -> vals[vi], fsq) ≈ 16
     fvq = MOI.VectorQuadraticFunction(MOI.VectorAffineTerm.([2, 1], MOI.ScalarAffineTerm.(1.0, [x, y])),
                                       MOI.VectorQuadraticTerm.([1, 2, 2], MOI.ScalarQuadraticTerm.(1.0, [x, w, w], [z, z, y])), [-3.0, -2.0])
     @test MOI.output_dimension(fvq) == 2
-    @test MOIU.evalvariables(vi -> vals[vi], fvq) ≈ [13, 1]
-    @test MOIU.evalvariables(vi -> vals[vi], fvq) ≈ [13, 1]
+    @test MOIU.eval_variables(vi -> vals[vi], fvq) ≈ [13, 1]
+    @test MOIU.eval_variables(vi -> vals[vi], fvq) ≈ [13, 1]
 end
 @testset "mapvariables" begin
     fsq = MOI.ScalarQuadraticFunction(MOI.ScalarAffineTerm.(1.0, [x, y]),
@@ -285,15 +285,15 @@ end
             @test f ≈ MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([3, 4], [x, y]), 5) - MOI.SingleVariable(x)
         end
         @testset "modification" begin
-            f = MOIU.modifyfunction(f, MOI.ScalarConstantChange(6))
+            f = MOIU.modify_function(f, MOI.ScalarConstantChange(6))
             @test f.constant == 6
             g = deepcopy(f)
             @test g ≈ f
-            f = MOIU.modifyfunction(f, MOI.ScalarCoefficientChange(y, 3))
+            f = MOIU.modify_function(f, MOI.ScalarCoefficientChange(y, 3))
             @test !(g ≈ f)
             @test g.terms == MOI.ScalarAffineTerm.([2, 4], [x, y])
             @test f.terms == MOI.ScalarAffineTerm.([2, 3], [x, y])
-            f = MOIU.modifyfunction(f, MOI.ScalarCoefficientChange(x, 0))
+            f = MOIU.modify_function(f, MOI.ScalarCoefficientChange(x, 0))
             @test f.terms == MOI.ScalarAffineTerm.([3], [y])
         end
     end
@@ -409,13 +409,13 @@ end
                                               MOI.ScalarQuadraticTerm.([1.0, 2.0, 3.0], [x, y, x], [x, y, y]), 7.0) / 2.0
         end
         @testset "modification" begin
-            f = MOIU.modifyfunction(f, MOI.ScalarConstantChange(9))
+            f = MOIU.modify_function(f, MOI.ScalarConstantChange(9))
             @test f.constant == 9
-            f = MOIU.modifyfunction(f, MOI.ScalarCoefficientChange(y, 0))
+            f = MOIU.modify_function(f, MOI.ScalarCoefficientChange(y, 0))
             @test f.affine_terms == MOI.ScalarAffineTerm.([3], [x])
             g = deepcopy(f)
             @test f ≈ g
-            f = MOIU.modifyfunction(f, MOI.ScalarCoefficientChange(y, 2))
+            f = MOIU.modify_function(f, MOI.ScalarCoefficientChange(y, 2))
             @test !(f ≈ g)
             @test g.affine_terms == MOI.ScalarAffineTerm.([3], [x])
             @test f.affine_terms == MOI.ScalarAffineTerm.([3, 2], [x, y])
@@ -430,26 +430,26 @@ end
         @test MOI.output_dimension(f) == 2
         @test f.terms == MOI.VectorAffineTerm.([1, 1, 2], MOI.ScalarAffineTerm.([2, 4, 3], [x, y, y]))
         @test MOIU.constant_vector(f) == [5, 7]
-        f = MOIU.modifyfunction(f, MOI.VectorConstantChange([6, 8]))
+        f = MOIU.modify_function(f, MOI.VectorConstantChange([6, 8]))
         @test MOIU.constant_vector(f) == [6, 8]
         g = deepcopy(f)
         @test f ≈ g
-        f = MOIU.modifyfunction(f, MOI.MultirowChange(y, [(2, 9)]))
+        f = MOIU.modify_function(f, MOI.MultirowChange(y, [(2, 9)]))
         @test !(f ≈ g)
         @test f.terms == MOI.VectorAffineTerm.([1, 1, 2], MOI.ScalarAffineTerm.([2, 4, 9], [x, y, y]))
         @test g.terms == MOI.VectorAffineTerm.([1, 1, 2], MOI.ScalarAffineTerm.([2, 4, 3], [x, y, y]))
-        f = MOIU.modifyfunction(f, MOI.MultirowChange(y, [(1, 0)]))
+        f = MOIU.modify_function(f, MOI.MultirowChange(y, [(1, 0)]))
         @test f.terms == MOI.VectorAffineTerm.([1, 2], MOI.ScalarAffineTerm.([2, 9], [x, y]))
     end
     @testset "Quadratic" begin
         f = MOI.VectorQuadraticFunction(MOI.VectorAffineTerm.([1, 2, 2], MOI.ScalarAffineTerm.([3, 1, 2], [x, x, y])), MOI.VectorQuadraticTerm.([1, 1, 2], MOI.ScalarQuadraticTerm.([1, 2, 3], [x, y, x], [x, y, y])), [7, 3, 4])
         @test MOI.output_dimension(f) == 3
-        f = MOIU.modifyfunction(f, MOI.VectorConstantChange([10, 11, 12]))
+        f = MOIU.modify_function(f, MOI.VectorConstantChange([10, 11, 12]))
         @test MOIU.constant_vector(f) == [10, 11, 12]
-        f = MOIU.modifyfunction(f, MOI.MultirowChange(y, [(2, 0), (1, 1)]))
+        f = MOIU.modify_function(f, MOI.MultirowChange(y, [(2, 0), (1, 1)]))
         @test f.affine_terms == MOI.VectorAffineTerm.([1, 2, 1], MOI.ScalarAffineTerm.([3, 1, 1], [x, x, y]))
         g = deepcopy(f)
-        f = MOIU.modifyfunction(f, MOI.MultirowChange(x, [(1, 0), (3, 4)]))
+        f = MOIU.modify_function(f, MOI.MultirowChange(x, [(1, 0), (3, 4)]))
         @test f.affine_terms == MOI.VectorAffineTerm.([2, 1, 3], MOI.ScalarAffineTerm.([1, 1, 4], [x, y, x]))
         @test g.affine_terms == MOI.VectorAffineTerm.([1, 2, 1], MOI.ScalarAffineTerm.([3, 1, 1], [x, x, y]))
     end
diff --git a/test/Utilities/model.jl b/test/Utilities/model.jl
index 78010f9a05..cb56f5e0e5 100644
--- a/test/Utilities/model.jl
+++ b/test/Utilities/model.jl
@@ -111,8 +111,8 @@ end
     @test (MOI.VectorQuadraticFunction{Int},MOI.PositiveSemidefiniteConeTriangle) in loc
     @test (MOI.VectorQuadraticFunction{Int},MOI.PositiveSemidefiniteConeTriangle) in loc
 
-    f3 = MOIU.modifyfunction(f1, MOI.ScalarConstantChange(9))
-    f3 = MOIU.modifyfunction(f3, MOI.ScalarCoefficientChange(y, 2))
+    f3 = MOIU.modify_function(f1, MOI.ScalarConstantChange(9))
+    f3 = MOIU.modify_function(f3, MOI.ScalarCoefficientChange(y, 2))
 
     @test !(MOI.get(model, MOI.ConstraintFunction(), c1) ≈ f3)
     MOI.set(model, MOI.ConstraintFunction(), c1, f3)

From 2f255f2b79eeef29f1295d3e2922c25d2de1ab4a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 18:21:29 -0400
Subject: [PATCH 07/12] iscanonical -> is_canonical

---
 docs/src/apireference.md    |  2 +-
 src/Utilities/functions.jl  |  4 ++--
 test/Utilities/functions.jl | 26 +++++++++++++-------------
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/docs/src/apireference.md b/docs/src/apireference.md
index 6193ef7be1..63b04692b9 100644
--- a/docs/src/apireference.md
+++ b/docs/src/apireference.md
@@ -626,7 +626,7 @@ Utilities.modifyfunction
 
 The following functions can be used to canonicalize a function:
 ```@docs
-Utilities.iscanonical
+Utilities.is_canonical
 Utilities.canonical
 Utilities.canonicalize!
 ```
diff --git a/src/Utilities/functions.jl b/src/Utilities/functions.jl
index 04b0c50ca6..b44d010aa1 100644
--- a/src/Utilities/functions.jl
+++ b/src/Utilities/functions.jl
@@ -204,13 +204,13 @@ function unsafe_add(t1::VT, t2::VT) where VT <: Union{MOI.VectorAffineTerm,
 end
 
 """
-    iscanonical(f::Union{ScalarAffineFunction, ScalarQuadraticFunction
+    is_canonical(f::Union{ScalarAffineFunction, ScalarQuadraticFunction
                          VectorAffineFunction, VectorQuadraticTerm})
 
 Returns a Bool indicating whether the function is in canonical form.
 See [`canonical`](@ref).
 """
-function iscanonical(f::Union{SAF, VAF, SQF, VQF})
+function is_canonical(f::Union{SAF, VAF, SQF, VQF})
     is_strictly_sorted(f.terms, MOI.term_indices,
                        t -> !iszero(MOI.coefficient(t)))
 end
diff --git a/test/Utilities/functions.jl b/test/Utilities/functions.jl
index 116c720efe..e8690850e9 100644
--- a/test/Utilities/functions.jl
+++ b/test/Utilities/functions.jl
@@ -461,20 +461,20 @@ end
          (MOI.coefficient.(f1.terms) ≈ MOI.coefficient.(f2.terms)))
     end
     function test_canonicalization(f::T, expected::T) where {T <: Union{MOI.ScalarAffineFunction, MOI.VectorAffineFunction}}
-        @test MOIU.iscanonical(expected)
+        @test MOIU.is_canonical(expected)
         g = @inferred(MOIU.canonical(f))
         @test isapprox_ordered(g, expected)
-        @test MOIU.iscanonical(g)
-        @test MOIU.iscanonical(expected)
+        @test MOIU.is_canonical(g)
+        @test MOIU.is_canonical(expected)
         @test isapprox_ordered(MOIU.canonical(g), g)
         @test MOIU.canonical(g) !== g
         @test @allocated(MOIU.canonicalize!(f)) == 0
     end
     @testset "ScalarAffine" begin
-        @test MOIU.iscanonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.(Float64[], MOI.VariableIndex.(Int[])), 1.0))
-        @test !MOIU.iscanonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([0.0], MOI.VariableIndex.([1])), 1.0))
-        @test !MOIU.iscanonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([1.0, 2.0], MOI.VariableIndex.([2, 1])), 2.0))
-        @test !MOIU.iscanonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([1.0, 0.0], MOI.VariableIndex.([1, 2])), 2.0))
+        @test MOIU.is_canonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.(Float64[], MOI.VariableIndex.(Int[])), 1.0))
+        @test !MOIU.is_canonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([0.0], MOI.VariableIndex.([1])), 1.0))
+        @test !MOIU.is_canonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([1.0, 2.0], MOI.VariableIndex.([2, 1])), 2.0))
+        @test !MOIU.is_canonical(MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.([1.0, 0.0], MOI.VariableIndex.([1, 2])), 2.0))
 
         test_canonicalization(
             MOI.ScalarAffineFunction(MOI.ScalarAffineTerm.(Float64[], MOI.VariableIndex[]), 1.5),
@@ -526,12 +526,12 @@ end
             )
     end
     @testset "VectorAffine" begin
-        @test MOIU.iscanonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.(Int[], MOI.ScalarAffineTerm.(Float64[], MOI.VariableIndex.(Int[]))), Float64[]))
-        @test !MOIU.iscanonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1], MOI.ScalarAffineTerm.([0.0], MOI.VariableIndex.([1]))), [1.0]))
-        @test !MOIU.iscanonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1, 2], MOI.ScalarAffineTerm.([0.0, 1.0], MOI.VariableIndex.([1, 2]))), [1.0]))
-        @test !MOIU.iscanonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([2, 1], MOI.ScalarAffineTerm.([1.0, 1.0], MOI.VariableIndex.([1, 2]))), [1.0]))
-        @test !MOIU.iscanonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1, 1], MOI.ScalarAffineTerm.([1.0, -1.0], MOI.VariableIndex.([1, 1]))), [1.0]))
-        @test !MOIU.iscanonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1, 1], MOI.ScalarAffineTerm.([1.0, 1.0], MOI.VariableIndex.([1, 1]))), [1.0]))
+        @test MOIU.is_canonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.(Int[], MOI.ScalarAffineTerm.(Float64[], MOI.VariableIndex.(Int[]))), Float64[]))
+        @test !MOIU.is_canonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1], MOI.ScalarAffineTerm.([0.0], MOI.VariableIndex.([1]))), [1.0]))
+        @test !MOIU.is_canonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1, 2], MOI.ScalarAffineTerm.([0.0, 1.0], MOI.VariableIndex.([1, 2]))), [1.0]))
+        @test !MOIU.is_canonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([2, 1], MOI.ScalarAffineTerm.([1.0, 1.0], MOI.VariableIndex.([1, 2]))), [1.0]))
+        @test !MOIU.is_canonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1, 1], MOI.ScalarAffineTerm.([1.0, -1.0], MOI.VariableIndex.([1, 1]))), [1.0]))
+        @test !MOIU.is_canonical(MOI.VectorAffineFunction(MOI.VectorAffineTerm.([1, 1], MOI.ScalarAffineTerm.([1.0, 1.0], MOI.VariableIndex.([1, 1]))), [1.0]))
 
         test_canonicalization(
             MOI.VectorAffineFunction(MOI.VectorAffineTerm.(Int[], MOI.ScalarAffineTerm.(Float64[], MOI.VariableIndex.(Int[]))), Float64[]),

From 53d0d7c951363b66f53344ff1d47adc602126f2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 18:23:22 -0400
Subject: [PATCH 08/12] Defined removing a variable

---
 src/indextypes.jl | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/indextypes.jl b/src/indextypes.jl
index 0a4560e909..9e82465f24 100644
--- a/src/indextypes.jl
+++ b/src/indextypes.jl
@@ -99,8 +99,8 @@ Delete the referenced object from the model. Throw [`DeleteNotAllowed`](@ref) if
 if `index` cannot be deleted.
 
 The following modifications also take effect if `Index` is [`VariableIndex`](@ref):
-* If `index` used in the objective function, it is removed from the function;
-  see [`Utilities.remove_variable`](@ref).
+* If `index` used in the objective function, it is removed from the function,
+  i.e., it is substituted for zero.
 * For each `func`-in-`set` constraint of the model:
   - If `func isa SingleVariable` and `func.variable == index` then the
     constraint is deleted.
@@ -110,8 +110,8 @@ The following modifications also take effect if `Index` is [`VariableIndex`](@re
       then the variable is removed from `func` and `set` is replaced by
       `update_dimension(set, MOI.dimension(set) - 1)`.
     * Otherwise, a [`DeleteNotAllowed`](@ref) error is thrown.
-  - Otherwise, the variable is removed from `func`; see
-    [`Utilities.remove_variable`](@ref).
+  - Otherwise, the variable is removed from `func`, i.e., it is substituted for
+    zero.
 """
 delete(model::ModelLike, index::Index) = throw(DeleteNotAllowed(index))
 

From e4665bf438b2e4abba1938262ca09bf16f74cf07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Sun, 14 Jul 2019 19:06:56 -0400
Subject: [PATCH 09/12] Fix

---
 docs/src/apireference.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/src/apireference.md b/docs/src/apireference.md
index 63b04692b9..149d236b14 100644
--- a/docs/src/apireference.md
+++ b/docs/src/apireference.md
@@ -621,7 +621,7 @@ Utilities.remove_variable
 Utilities.all_coefficients
 Utilities.unsafe_add
 Utilities.isapprox_zero
-Utilities.modifyfunction
+Utilities.modify_function
 ```
 
 The following functions can be used to canonicalize a function:

From b44d3c8f392e2f04fe2f324ea764f90c11eb7175 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Tue, 16 Jul 2019 22:09:50 -0600
Subject: [PATCH 10/12] got -> queried

---
 src/Utilities/universalfallback.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Utilities/universalfallback.jl b/src/Utilities/universalfallback.jl
index e135186ddc..2f9d55bb5a 100644
--- a/src/Utilities/universalfallback.jl
+++ b/src/Utilities/universalfallback.jl
@@ -286,7 +286,7 @@ function MOI.get(uf::UniversalFallback, ::Type{CI{F, S}}, name::String) where {F
     if MOI.supports_constraint(uf.model, F, S)
         ci = MOI.get(uf.model, CI{F, S}, name)
     else
-        # There is no `F`-in-`S` constraint in `b.model`, `ci` is only got
+        # There is no `F`-in-`S` constraint in `b.model`, `ci` is only queried
         # to check for duplicate names.
         ci = MOI.get(uf.model, CI, name)
     end

From 6da195df9d9b4a57f3cadbcd0d882afda84ea078 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Tue, 16 Jul 2019 22:12:28 -0600
Subject: [PATCH 11/12] Add missing delete

---
 src/Utilities/model.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Utilities/model.jl b/src/Utilities/model.jl
index 47ff2803b1..70682cc093 100644
--- a/src/Utilities/model.jl
+++ b/src/Utilities/model.jl
@@ -194,6 +194,8 @@ function MOI.delete(model::AbstractModel{T}, vi::VI) where T
     delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.Interval{T}}(vi.value))
     delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.Integer}(vi.value))
     delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.ZeroOne}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.Semicontinuous{T}}(vi.value))
+    delete!(model.con_to_name, MOI.ConstraintIndex{MOI.SingleVariable, MOI.Semiinteger{T}}(vi.value))
 end
 function MOI.delete(model::AbstractModel, vis::Vector{VI})
     # Delete `VectorOfVariables(vis)` constraints as otherwise, it will error
@@ -400,6 +402,8 @@ single_variable_flag(::Type{MOI.Integer}) = 0x10
 single_variable_flag(::Type{MOI.ZeroOne}) = 0x20
 single_variable_flag(::Type{<:MOI.Semicontinuous}) = 0x40
 single_variable_flag(::Type{<:MOI.Semiinteger}) = 0x80
+# If a set is added here, a line should be added in
+# `MOI.delete(::AbstractModel, ::MOI.VariableIndex)`
 
 function flag_to_set_type(flag::UInt8, T::Type)
     if flag == 0x1

From b54ae5deb5b3875e07685df8f58c26cae07a9d35 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Tue, 16 Jul 2019 22:22:03 -0600
Subject: [PATCH 12/12] Move dimension update to MOI

---
 docs/src/apireference.md           |  4 ++--
 src/Test/modellike.jl              | 32 ++++++++++++++++++++++++++++++
 src/Utilities/model.jl             |  4 ++--
 src/Utilities/sets.jl              | 31 -----------------------------
 src/Utilities/universalfallback.jl |  2 +-
 src/sets.jl                        | 32 ++++++++++++++++++++++++++++++
 6 files changed, 69 insertions(+), 36 deletions(-)

diff --git a/docs/src/apireference.md b/docs/src/apireference.md
index 149d236b14..f6a069f230 100644
--- a/docs/src/apireference.md
+++ b/docs/src/apireference.md
@@ -254,6 +254,8 @@ Functions for getting properties of sets.
 ```@docs
 dimension
 constant(s::EqualTo)
+supports_dimension_update
+update_dimension
 ```
 
 ### Scalar sets
@@ -644,8 +646,6 @@ Utilities.vectorize
 
 The following utilities are available for sets:
 ```@docs
-Utilities.supports_dimension_update
-Utilities.update_dimension
 Utilities.shift_constant
 ```
 
diff --git a/src/Test/modellike.jl b/src/Test/modellike.jl
index c54b5947b3..7c4853df2e 100644
--- a/src/Test/modellike.jl
+++ b/src/Test/modellike.jl
@@ -488,6 +488,13 @@ function delete_test(model::MOI.ModelLike)
     @test MOI.get(model, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
     @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y)
     @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(4)
+    @test Set(MOI.get(model, MOI.ListOfConstraints())) ==
+        Set([(MOI.SingleVariable, MOI.GreaterThan{Float64}),
+             (MOI.VectorOfVariables, MOI.Nonpositives)])
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.SingleVariable, MOI.GreaterThan{Float64}}()) == [cx]
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.VectorOfVariables, MOI.Nonpositives}()) == [cy]
     MOI.delete(model, y[3])
     @test MOI.is_valid(model, x)
     @test MOI.is_valid(model, y[1])
@@ -500,6 +507,13 @@ function delete_test(model::MOI.ModelLike)
     @test MOI.get(model, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
     @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[1, 2, 4]])
     @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(3)
+    @test Set(MOI.get(model, MOI.ListOfConstraints())) ==
+        Set([(MOI.SingleVariable, MOI.GreaterThan{Float64}),
+             (MOI.VectorOfVariables, MOI.Nonpositives)])
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.SingleVariable, MOI.GreaterThan{Float64}}()) == [cx]
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.VectorOfVariables, MOI.Nonpositives}()) == [cy]
     MOI.delete(model, y[1])
     @test MOI.is_valid(model, x)
     @test !MOI.is_valid(model, y[1])
@@ -512,6 +526,13 @@ function delete_test(model::MOI.ModelLike)
     @test MOI.get(model, MOI.ConstraintSet(), cx) == MOI.GreaterThan(0.0)
     @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
     @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
+    @test Set(MOI.get(model, MOI.ListOfConstraints())) ==
+        Set([(MOI.SingleVariable, MOI.GreaterThan{Float64}),
+             (MOI.VectorOfVariables, MOI.Nonpositives)])
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.SingleVariable, MOI.GreaterThan{Float64}}()) == [cx]
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.VectorOfVariables, MOI.Nonpositives}()) == [cy]
     MOI.delete(model, x)
     @test !MOI.is_valid(model, x)
     @test !MOI.is_valid(model, y[1])
@@ -522,6 +543,12 @@ function delete_test(model::MOI.ModelLike)
     @test MOI.is_valid(model, cy)
     @test MOI.get(model, MOI.ConstraintFunction(), cy) == MOI.VectorOfVariables(y[[2, 4]])
     @test MOI.get(model, MOI.ConstraintSet(), cy) == MOI.Nonpositives(2)
+    @test MOI.get(model, MOI.ListOfConstraints()) ==
+        [(MOI.VectorOfVariables, MOI.Nonpositives)]
+    @test isempty(MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.SingleVariable, MOI.GreaterThan{Float64}}()))
+    @test MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.VectorOfVariables, MOI.Nonpositives}()) == [cy]
     MOI.delete(model, y[[2, 4]])
     @test !MOI.is_valid(model, x)
     @test !MOI.is_valid(model, y[1])
@@ -530,4 +557,9 @@ function delete_test(model::MOI.ModelLike)
     @test !MOI.is_valid(model, y[4])
     @test !MOI.is_valid(model, cx)
     @test !MOI.is_valid(model, cy)
+    @test isempty(MOI.get(model, MOI.ListOfConstraints()))
+    @test isempty(MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.SingleVariable, MOI.GreaterThan{Float64}}()))
+    @test isempty(MOI.get(model, MOI.ListOfConstraintIndices{
+        MOI.VectorOfVariables, MOI.Nonpositives}()))
 end
diff --git a/src/Utilities/model.jl b/src/Utilities/model.jl
index 70682cc093..165ebe50be 100644
--- a/src/Utilities/model.jl
+++ b/src/Utilities/model.jl
@@ -115,7 +115,7 @@ remove_variable(f, s, vi::VI) = remove_variable(f, vi), s
 function remove_variable(f::MOI.VectorOfVariables, s, vi::VI)
     g = remove_variable(f, vi)
     if length(g.variables) != length(f.variables)
-        t = update_dimension(s, length(g.variables))
+        t = MOI.update_dimension(s, length(g.variables))
     else
         t = s
     end
@@ -144,7 +144,7 @@ function _vector_of_variables_with(
             if length(f.variables) > 1
                 # If `supports_dimension_update(s)` then the variable will be
                 # removed in `_remove_variable`.
-                if !supports_dimension_update(typeof(s))
+                if !MOI.supports_dimension_update(typeof(s))
                     throw_delete_variable_in_vov(vi)
                 end
             else
diff --git a/src/Utilities/sets.jl b/src/Utilities/sets.jl
index aa6e178def..f23ed8c604 100644
--- a/src/Utilities/sets.jl
+++ b/src/Utilities/sets.jl
@@ -1,34 +1,3 @@
-"""
-    supports_dimension_update(S::Type{<:MOI.AbstractVectorSet})
-
-Return a `Bool` indicating whether the elimination of any dimension of
-`n`-dimensional sets of type `S` give an `n-1`-dimensional set `S`.
-By default, this function returns `false` so it should only be implemented
-for sets that supports dimension update.
-
-For instance, `supports_dimension_update(MOI.Nonnegatives}` is `true` because
-the elimination of any dimension of the `n`-dimensional nonnegative orthant
-gives the `n-1`-dimensional nonnegative orthant. However
-`supports_dimension_update(MOI.ExponentialCone}` is `false`.
-"""
-function supports_dimension_update(::Type{<:MOI.AbstractVectorSet})
-    return false
-end
-function supports_dimension_update(::Type{<:Union{
-    MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives}})
-    return true
-end
-
-"""
-    update_dimension(s::AbstractVectorSet, new_dim)
-
-Returns a set with the dimension modified to `new_dim`.
-"""
-function update_dimension(set::Union{
-    MOI.Reals, MOI.Zeros, MOI.Nonnegatives, MOI.Nonpositives}, new_dim)
-    return typeof(set)(new_dim)
-end
-
 """
     shift_constant(set::MOI.AbstractScalarSet,
                    offset)
diff --git a/src/Utilities/universalfallback.jl b/src/Utilities/universalfallback.jl
index 2f9d55bb5a..c548e92a58 100644
--- a/src/Utilities/universalfallback.jl
+++ b/src/Utilities/universalfallback.jl
@@ -99,7 +99,7 @@ function _remove_variable(uf::UniversalFallback,
         f::MOI.VectorOfVariables, s = constraint
         if vi in f.variables
             if length(f.variables) > 1
-                if supports_dimension_update(S)
+                if MOI.supports_dimension_update(S)
                     constraints[ci] = remove_variable(f, s, vi)
                 else
                     throw_delete_variable_in_vov(vi)
diff --git a/src/sets.jl b/src/sets.jl
index b785106ed8..61e2b73681 100644
--- a/src/sets.jl
+++ b/src/sets.jl
@@ -591,3 +591,35 @@ function Base.copy(set::Union{Reals, Zeros, Nonnegatives, Nonpositives,
     return set
 end
 Base.copy(set::S) where {S <: Union{SOS1, SOS2}} = S(copy(set.weights))
+
+"""
+    supports_dimension_update(S::Type{<:MOI.AbstractVectorSet})
+
+Return a `Bool` indicating whether the elimination of any dimension of
+`n`-dimensional sets of type `S` give an `n-1`-dimensional set `S`.
+By default, this function returns `false` so it should only be implemented
+for sets that supports dimension update.
+
+For instance, `supports_dimension_update(MOI.Nonnegatives}` is `true` because
+the elimination of any dimension of the `n`-dimensional nonnegative orthant
+gives the `n-1`-dimensional nonnegative orthant. However
+`supports_dimension_update(MOI.ExponentialCone}` is `false`.
+"""
+function supports_dimension_update(::Type{<:AbstractVectorSet})
+    return false
+end
+function supports_dimension_update(::Type{<:Union{
+    Reals, Zeros, Nonnegatives, Nonpositives}})
+    return true
+end
+
+"""
+    update_dimension(s::AbstractVectorSet, new_dim)
+
+Returns a set with the dimension modified to `new_dim`.
+"""
+function update_dimension end
+function update_dimension(set::Union{
+    Reals, Zeros, Nonnegatives, Nonpositives}, new_dim)
+    return typeof(set)(new_dim)
+end