implement dictionary of variable names and getVar, closes #399

NEWS.md

@@ -7,6 +7,7 @@ Unversioned
   * Support for conditions in indexing ``@defVar`` and ``@addConstraint`` constructs, e.g. ``@defVar(m, x[i=1:5,j=1:5; i+j >= 3])``
   * Support for vectorized operations on Variables, expressions, and JuMPArrays with indexing over unit-step ranges starting at one. See
     the documentation for details.
+  * New ``getVar()`` method to access variables in a model by name
 
 Version 0.9.1 (April 25, 2015)
 ------------------------------

doc/refmodel.rst

@@ -46,6 +46,7 @@ Methods
 * ``solve(m::Model;  suppress_warnings=false)`` - solves the model using the selected solver (or a default for the problem class), and takes two optional arguments that are disabled by default. Setting ``suppress_warnings`` to ``true`` will suppress all JuMP-specific output (e.g. warnings about infeasibility and lack of dual information) but will not suppress solver output (which should be done by passing options to the solver).
 * ``buildInternalModel(m::Model)`` - builds the model in memory at the MathProgBase level without optimizing.
 * ``setSolver(m::Model,s::AbstractMathProgSolver)`` - changes the solver which will be used for the next call to ``solve()``, discarding the current internal model if present.
+* ``getVar(m::Model,name::Symbol)`` - returns the variable or group of variables of the given name which were added to the model with ``@defVar``. Throws an error if multiple variables were created with the same name.
 
 **Objective**
 

src/JuMP.jl

@@ -32,6 +32,7 @@ export
     # Variable
     setName, getName, setLower, setUpper, getLower, getUpper,
     getValue, setValue, getDual, setCategory, getCategory,
+    getVar,
     # Expressions and constraints
     affToStr, quadToStr, conToStr, chgConstrRHS,
 
@@ -95,6 +96,8 @@ type Model
 
     nlpdata#::NLPData
 
+    varDict::Dict{Symbol,Any} # dictionary from variable names to variable objects
+
     # Extension dictionary - e.g. for robust
     # Extensions should define a type to hold information particular to
     # their functionality, and store an instance of the type in this
@@ -115,7 +118,7 @@ function Model(;solver=UnsetSolver())
           0,String[],String[],Float64[],Float64[],Symbol[],
           0,Float64[],Float64[],Float64[],nothing,solver,
           false,Any[],nothing,nothing,JuMPContainer[],
-          IndexedVector(Float64,0),nothing,Dict{Symbol,Any}())
+          IndexedVector(Float64,0),nothing,Dict{Symbol,Any}(),Dict{Symbol,Any}())
 end
 
 # Getters/setters
@@ -730,6 +733,28 @@ function Variable(m::Model,lower::Number,upper::Number,cat::Symbol,objcoef::Numb
     return v
 end
 
+# handle dictionary of variables
+function registervar(m::Model, varname::Symbol, value)
+    if haskey(m.varDict, varname)
+        m.varDict[varname] = nothing # indicate duplicate variable
+    else
+        m.varDict[varname] = value
+    end
+    return value
+end
+registervar(m::Model, varname, value) = value # variable name isn't a simple symbol, ignore
+
+function getVar(m::Model, varname::Symbol)
+    if !haskey(m.varDict, varname)
+        error("No variable with name $varname")
+    elseif m.varDict[varname] === nothing
+        error("Multiple variables with name $varname")
+    else
+        return m.varDict[varname]
+    end
+end
+
+
 ##########################################################################
 # Operator overloads
 include("operators.jl")

src/macros.jl

@@ -699,6 +699,7 @@ macro defVar(args...)
         # Easy case - a single variable
         return assert_validmodel(m, quote
             $(esc(var)) = Variable($m,$lb,$ub,$(quot(t)),$(string(var)),$value)
+            registervar($m, $(quot(var)), $(esc(var)))
         end)
     end
     isa(var,Expr) || error("in @defVar: expected $var to be a variable name")
@@ -712,7 +713,7 @@ macro defVar(args...)
     return assert_validmodel(m, quote
         $looped
         push!($(m).dictList, $varname)
-        $varname
+        registervar($m, $(quot(getname(var))), $varname)
     end)
 end
 

test/variable.jl

@@ -27,6 +27,15 @@ facts("[variable] constructors") do
     @defVar(mcon, x[i=-10:10,s] <= 5.5, Int, start=i+1)
     @fact getUpper(x[-4,"Green"]) => 5.5
     @fact getValue(x[-3,"Blue"]) => -2
+    @fact isequal(getVar(mcon, :lbonly),lbonly) => true
+    @fact isequal(getVar(mcon, :ubonly),ubonly) => true
+    @fact isequal(getVar(mcon, :onerangeub)[-7],onerangeub[-7]) => true
+    @defVar(mcon, lbonly)
+    @fact_throws ErrorException getVar(mcon, :lbonly)
+    @fact_throws ErrorException getVar(mcon, :foo)
+    d = Dict()
+    @defVar(mcon, d["bar"][1:10] == 1)
+    @fact getValue(d["bar"][1]) => 1
 end
 
 facts("[variable] get and set bounds") do