Remove SingleVariable

src/FileFormats/NL/NLExpr.jl

@@ -296,8 +296,6 @@ end
 
 _NLExpr(x::MOI.VariableIndex) = _NLExpr(true, _NLTerm[], Dict(x => 1.0), 0.0)
 
-_NLExpr(x::MOI.SingleVariable) = _NLExpr(x.variable)
-
 function _add_or_set(dict, key, value)
     if haskey(dict, key)
         dict[key] += value

src/MathOptInterface.jl

@@ -159,6 +159,22 @@ is_valid(dest, index_map[x]) # true
 """
 function copy_to end
 
+import MutableArithmetics
+
+"""
+    AbstractFunction
+
+Abstract supertype for function objects.
+"""
+abstract type AbstractFunction <: MutableArithmetics.AbstractMutable end
+
+"""
+    AbstractScalarFunction
+
+Abstract supertype for scalar-valued function objects.
+"""
+abstract type AbstractScalarFunction <: AbstractFunction end
+
 include("error.jl")
 include("indextypes.jl")
 include("functions.jl")

src/Utilities/functions.jl

@@ -156,10 +156,6 @@ end
 
 # Functions
 
-function map_indices(index_map::F, f::MOI.SingleVariable) where {F<:Function}
-    return MOI.SingleVariable(index_map(f.variable))
-end
-
 function map_indices(index_map::F, f::MOI.VectorOfVariables) where {F<:Function}
     return MOI.VectorOfVariables(index_map.(f.variables))
 end

src/Utilities/print.jl

@@ -111,14 +111,6 @@ function _shorten(options::_PrintOptions, x::Float64)
     return string(x)
 end
 
-function _to_string(
-    options::_PrintOptions,
-    model::MOI.ModelLike,
-    f::MOI.SingleVariable,
-)
-    return _to_string(options, model, f.variable)
-end
-
 """
     _to_string(options::_PrintOptions, c::Float64, x::String)
 

src/Utilities/results.jl

@@ -444,21 +444,12 @@ end
 
 """
     variable_dual(model::MOI.ModelLike, attr::MOI.ConstraintDual,
-                  ci::MOI.ConstraintIndex{F},
-                  func::F) where F <: Union{MOI.SingleVariable,
-                                            MOI.VectorOfVariables}
+                  ci::MOI.ConstraintIndex{MOI.VectorOfVariables},
+                  func::MOI.VectorOfVariables)
 
 Return the dual of the constraint of index `ci` for which the value of the
 `MOI.ConstraintFunction` attribute is `func`.
 """
-function variable_dual(
-    model::MOI.ModelLike,
-    attr::MOI.ConstraintDual,
-    ci::MOI.ConstraintIndex{MOI.SingleVariable},
-    func::MOI.SingleVariable,
-)
-    return variable_dual(model, attr, ci, func.variable)
-end
 function variable_dual(
     model::MOI.ModelLike,
     attr::MOI.ConstraintDual,

src/constraints.jl

@@ -207,13 +207,6 @@ function correct_throw_add_constraint_error_fallback(
 end
 
 # convenient shorthands TODO: document
-function add_constraint(
-    model::ModelLike,
-    v::VariableIndex,
-    set::AbstractScalarSet,
-)
-    return add_constraint(model, SingleVariable(v), set)
-end
 function add_constraint(
     model::ModelLike,
     v::Vector{VariableIndex},

src/functions.jl

@@ -1,14 +1,5 @@
 # Functions
 
-import MutableArithmetics
-
-"""
-    AbstractFunction
-
-Abstract supertype for function objects.
-"""
-abstract type AbstractFunction <: MutableArithmetics.AbstractMutable end
-
 """
     output_dimension(f::AbstractFunction)
 
@@ -17,12 +8,6 @@ has a vector output.
 """
 function output_dimension end
 
-"""
-    AbstractScalarFunction
-
-Abstract supertype for scalar-valued function objects.
-"""
-abstract type AbstractScalarFunction <: AbstractFunction end
 output_dimension(::AbstractScalarFunction) = 1
 
 Base.broadcastable(f::AbstractScalarFunction) = Ref(f)
@@ -42,8 +27,15 @@ abstract type AbstractVectorFunction <: AbstractFunction end
 The function that extracts the scalar variable referenced by `variable`, a `VariableIndex`.
 This function is naturally be used for single variable bounds or integrality constraints.
 """
-struct SingleVariable <: AbstractScalarFunction
-    variable::VariableIndex
+const SingleVariable = VariableIndex
+VariableIndex(vi::VariableIndex) = vi
+function Base.getproperty(vi::VariableIndex, s::Symbol)
+    if s === :value
+        return getfield(vi, s)
+    else
+        @assert s === :variable
+        return vi
+    end
 end
 
 """

src/indextypes.jl

@@ -27,7 +27,7 @@ index_value(ci::ConstraintIndex) = ci.value
 A type-safe wrapper for `Int64` for use in referencing variables in a model.
 To allow for deletion, indices need not be consecutive.
 """
-struct VariableIndex
+struct VariableIndex <: AbstractScalarFunction
     value::Int64
 end
 index_value(vi::VariableIndex) = vi.value

test/Bridges/lazy_bridge_optimizer.jl

@@ -930,8 +930,8 @@ Objective function of type `MOI.ScalarQuadraticFunction{$T}` is not supported an
    Cannot use `$(MOI.Bridges.Objective.SlackBridge{T,MOI.ScalarQuadraticFunction{T},MOI.ScalarQuadraticFunction{T}})` because:
    (1) `MOI.ScalarQuadraticFunction{$T}`-in-`MOI.GreaterThan{$T}` constraints are not supported
    (2) `MOI.ScalarQuadraticFunction{$T}`-in-`MOI.LessThan{$T}` constraints are not supported
-   |2| objective function of type `MOI.SingleVariable` is not supported
- |2| objective function of type `MOI.SingleVariable` is not supported because no added bridge supports bridging it.
+   |2| objective function of type `MOI.VariableIndex` is not supported
+ |2| objective function of type `MOI.VariableIndex` is not supported because no added bridge supports bridging it.
 """,
         )
         MOI.Bridges.add_bridge(
@@ -1021,14 +1021,14 @@ Objective function of type `MOI.ScalarQuadraticFunction{$T}` is not supported an
               MOI.Utilities.replace_acronym(
             """
 Bridge graph with 1 variable nodes, 5 constraint nodes and 2 objective nodes.
- [1] constrained variables in `MOI.RotatedSecondOrderCone` are bridged (distance 2) by $(MOI.Bridges.Variable.RSOCtoPSDBridge{T}).
- (1) `MOI.ScalarQuadraticFunction{$T}`-in-`MOI.GreaterThan{$T}` constraints are bridged (distance 5) by $(MOI.Bridges.Constraint.QuadtoSOCBridge{T}).
- (2) `MOI.VectorAffineFunction{$T}`-in-`MOI.RotatedSecondOrderCone` constraints are bridged (distance 4) by $(MOI.Bridges.Constraint.VectorSlackBridge{T,MOI.VectorAffineFunction{T},MOI.RotatedSecondOrderCone}).
- (3) `MOI.SingleVariable`-in-`MOI.EqualTo{$T}` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.ScalarFunctionizeBridge{T,MOI.EqualTo{T}}).
- (4) `MOI.VectorAffineFunction{$T}`-in-`MOI.Zeros` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.ScalarizeBridge{T,MOI.ScalarAffineFunction{T},MOI.EqualTo{T}}).
- (5) `MOI.ScalarQuadraticFunction{$T}`-in-`MOI.LessThan{$T}` constraints are bridged (distance 5) by $(MOI.Bridges.Constraint.QuadtoSOCBridge{T}).
- |1| objective function of type `MOI.ScalarQuadraticFunction{$T}` is bridged (distance 12) by $(MOI.Bridges.Objective.SlackBridge{T,MOI.ScalarQuadraticFunction{T},MOI.ScalarQuadraticFunction{T}}).
- |2| objective function of type `MOI.SingleVariable` is bridged (distance 1) by $(MOI.Bridges.Objective.FunctionizeBridge{T}).
+ [1] constrained variables in `MOI.RotatedSecondOrderCone` are bridged (distance 2) by $(MOIB.Variable.RSOCtoPSDBridge{T}).
+ (1) `MOI.ScalarQuadraticFunction{$T}`-in-`MOI.GreaterThan{$T}` constraints are bridged (distance 5) by $(MOIB.Constraint.QuadtoSOCBridge{T}).
+ (2) `MOI.VectorAffineFunction{$T}`-in-`MOI.RotatedSecondOrderCone` constraints are bridged (distance 4) by $(MOIB.Constraint.VectorSlackBridge{T,MOI.VectorAffineFunction{T},MOI.RotatedSecondOrderCone}).
+ (3) `MOI.VariableIndex`-in-`MOI.EqualTo{$T}` constraints are bridged (distance 1) by $(MOIB.Constraint.ScalarFunctionizeBridge{T,MOI.EqualTo{T}}).
+ (4) `MOI.VectorAffineFunction{$T}`-in-`MOI.Zeros` constraints are bridged (distance 1) by $(MOIB.Constraint.ScalarizeBridge{T,MOI.ScalarAffineFunction{T},MOI.EqualTo{T}}).
+ (5) `MOI.ScalarQuadraticFunction{$T}`-in-`MOI.LessThan{$T}` constraints are bridged (distance 5) by $(MOIB.Constraint.QuadtoSOCBridge{T}).
+ |1| objective function of type `MOI.ScalarQuadraticFunction{$T}` is bridged (distance 12) by $(MOIB.Objective.SlackBridge{T,MOI.ScalarQuadraticFunction{T},MOI.ScalarQuadraticFunction{T}}).
+ |2| objective function of type `MOI.VariableIndex` is bridged (distance 1) by $(MOIB.Objective.FunctionizeBridge{T}).
 """,
         )
     end
@@ -1273,12 +1273,12 @@ Bridge graph with 5 variable nodes, 11 constraint nodes and 0 objective nodes.
  (3) `MOI.VectorOfVariables`-in-`MOI.RotatedSecondOrderCone` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.RSOCtoSOCBridge{T,MOI.VectorAffineFunction{T},MOI.VectorOfVariables}).
  (4) `MOI.VectorAffineFunction{$T}`-in-`MOI.PositiveSemidefiniteConeTriangle` constraints are not supported
  (5) `MOI.VectorOfVariables`-in-`MOI.PositiveSemidefiniteConeTriangle` constraints are not supported
- (6) `MOI.VectorOfVariables`-in-`MOI.Nonnegatives` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.NonnegToNonposBridge{T,MOI.VectorAffineFunction{T},MOI.VectorOfVariables}).
- (7) `MOI.SingleVariable`-in-`MOI.GreaterThan{$T}` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.GreaterToLessBridge{T,MOI.ScalarAffineFunction{T},MOI.SingleVariable}).
- (8) `MOI.SingleVariable`-in-`MOI.Interval{$T}` constraints are bridged (distance 2) by $(MOI.Bridges.Constraint.ScalarFunctionizeBridge{T,MOI.Interval{T}}).
- (9) `MOI.ScalarAffineFunction{$T}`-in-`MOI.Interval{$T}` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.SplitIntervalBridge{T,MOI.ScalarAffineFunction{T},MOI.Interval{T},MOI.GreaterThan{T},MOI.LessThan{T}}).
- (10) `MOI.SingleVariable`-in-`MOI.LessThan{$T}` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.LessToGreaterBridge{T,MOI.ScalarAffineFunction{T},MOI.SingleVariable}).
- (11) `MOI.SingleVariable`-in-`MOI.EqualTo{$T}` constraints are bridged (distance 1) by $(MOI.Bridges.Constraint.VectorizeBridge{T,MOI.VectorAffineFunction{T},MOI.Zeros,MOI.SingleVariable}).
+ (6) `MOI.VectorOfVariables`-in-`MOI.Nonnegatives` constraints are bridged (distance 1) by $(MOIB.Constraint.NonnegToNonposBridge{T,MOI.VectorAffineFunction{T},MOI.VectorOfVariables}).
+ (7) `MOI.VariableIndex`-in-`MOI.GreaterThan{$T}` constraints are bridged (distance 1) by $(MOIB.Constraint.GreaterToLessBridge{T,MOI.ScalarAffineFunction{T},MOI.SingleVariable}).
+ (8) `MOI.VariableIndex`-in-`MOI.Interval{$T}` constraints are bridged (distance 2) by $(MOIB.Constraint.ScalarFunctionizeBridge{T,MOI.Interval{T}}).
+ (9) `MOI.ScalarAffineFunction{$T}`-in-`MOI.Interval{$T}` constraints are bridged (distance 1) by $(MOIB.Constraint.SplitIntervalBridge{T,MOI.ScalarAffineFunction{T},MOI.Interval{T},MOI.GreaterThan{T},MOI.LessThan{T}}).
+ (10) `MOI.VariableIndex`-in-`MOI.LessThan{$T}` constraints are bridged (distance 1) by $(MOIB.Constraint.LessToGreaterBridge{T,MOI.ScalarAffineFunction{T},MOI.SingleVariable}).
+ (11) `MOI.VariableIndex`-in-`MOI.EqualTo{$T}` constraints are bridged (distance 1) by $(MOIB.Constraint.VectorizeBridge{T,MOI.VectorAffineFunction{T},MOI.Zeros,MOI.SingleVariable}).
 """,
     )
     return

test/Utilities/print.jl

@@ -212,7 +212,7 @@ function test_min()
     model = MOIU.Model{Float64}()
     MOIU.loadfromstring!(model, "variables: x\nminobjective: x")
     @test sprint(print, model) == """
-    Minimize SingleVariable:
+    Minimize VariableIndex:
      x
 
     Subject to:
@@ -232,7 +232,7 @@ function test_max()
     model = MOIU.Model{Float64}()
     MOIU.loadfromstring!(model, "variables: x\nmaxobjective: x")
     @test sprint(print, model) == """
-    Maximize SingleVariable:
+    Maximize VariableIndex:
      x
 
     Subject to:
@@ -312,13 +312,13 @@ function test_model()
      │0.0 + 1.0 y │
      └            ┘ $(IN) ExponentialCone()
 
-    SingleVariable-in-GreaterThan{Float64}
+    VariableIndex-in-GreaterThan{Float64}
      x >= 0.1
 
-    SingleVariable-in-Integer
+    VariableIndex-in-Integer
      z $(IN) ℤ
 
-    SingleVariable-in-ZeroOne
+    VariableIndex-in-ZeroOne
      x $(IN) {0, 1}
      y $(IN) {0, 1}
     """
@@ -379,11 +379,11 @@ function test_latex()
         1.0\\
         0.0 + 1.0 x^2\\
         0.0 + 1.0 y\end{bmatrix} \in \text{ExponentialCone()} \\
-         & \text{SingleVariable-in-GreaterThan{Float64}} \\
+         & \text{VariableIndex-in-GreaterThan{Float64}} \\
          & x \ge 0.1 \\
-         & \text{SingleVariable-in-Integer} \\
+         & \text{VariableIndex-in-Integer} \\
          & z \in \mathbb{Z} \\
-         & \text{SingleVariable-in-ZeroOne} \\
+         & \text{VariableIndex-in-ZeroOne} \\
          & x \in \{0, 1\} \\
          & y \in \{0, 1\} \\
         \end{aligned} $$""",
@@ -544,13 +544,13 @@ function test_nlp()
 
     Subject to:
 
-    SingleVariable-in-GreaterThan{Float64}
+    VariableIndex-in-GreaterThan{Float64}
      x[1] >= 1.1
      x[2] >= 1.2
      x[3] >= 1.3
      x[4] >= 1.4
 
-    SingleVariable-in-LessThan{Float64}
+    VariableIndex-in-LessThan{Float64}
      x[1] <= 5.1
      x[2] <= 5.2
      x[3] <= 5.3
@@ -566,12 +566,12 @@ function test_nlp()
         $$ \begin{aligned}
         \min\quad & x_{1} \times x_{4} \times (x_{1} + x_{2} + x_{3}) + x_{3} \\
         \text{Subject to}\\
-         & \text{SingleVariable-in-GreaterThan{Float64}} \\
+         & \text{VariableIndex-in-GreaterThan{Float64}} \\
          & x_{1} \ge 1.1 \\
          & x_{2} \ge 1.2 \\
          & x_{3} \ge 1.3 \\
          & x_{4} \ge 1.4 \\
-         & \text{SingleVariable-in-LessThan{Float64}} \\
+         & \text{VariableIndex-in-LessThan{Float64}} \\
          & x_{1} \le 5.1 \\
          & x_{2} \le 5.2 \\
          & x_{3} \le 5.3 \\

test/errors.jl

@@ -52,7 +52,7 @@ function _test_errors_UnsupportedConstraint(f)
     catch err
         @test sprint(showerror, err) ==
               "$(MOI.UnsupportedConstraint{MOI.SingleVariable,MOI.EqualTo{Int}}):" *
-              " `$MOI.SingleVariable`-in-`$MOI.EqualTo{$Int}` constraint is" *
+              " `$MOI.VariableIndex`-in-`$MOI.EqualTo{$Int}` constraint is" *
               " not supported by the model."
     end
     return
@@ -90,7 +90,7 @@ function test_errors_add_constraint()
     catch err
         @test sprint(showerror, err) ==
               "$(MOI.AddConstraintNotAllowed{MOI.SingleVariable,MOI.EqualTo{Float64}}):" *
-              " Adding `$MOI.SingleVariable`-in-`$MOI.EqualTo{Float64}`" *
+              " Adding `$MOI.VariableIndex`-in-`$MOI.EqualTo{Float64}`" *
               " constraints cannot be performed. You may want to use a" *
               " `CachingOptimizer` in `AUTOMATIC` mode or you may need to call" *
               " `reset_optimizer` before doing this operation if the" *