Add Variable map

src/Bridges/Bridges.jl

@@ -9,6 +9,8 @@ const CI = MOI.ConstraintIndex
 include("bridge.jl")
 include("bridge_optimizer.jl")
 
+# Variable bridges
+include("Variable/Variable.jl")
 # Constraint bridges
 include("Constraint/Constraint.jl")
 

src/Bridges/Variable/Variable.jl

@@ -0,0 +1,14 @@
+module Variable
+
+using MathOptInterface
+const MOI = MathOptInterface
+const MOIU = MOI.Utilities
+const MOIB = MOI.Bridges
+
+# Definition of a variable bridge
+include("bridge.jl")
+
+# Mapping between variable indices and bridges
+include("map.jl")
+
+end

src/Bridges/Variable/bridge.jl

@@ -155,3 +155,24 @@ function concrete_bridge_type(b::MOIB.AbstractBridgeOptimizer,
                               S::Type{<:MOI.AbstractSet})
     return concrete_bridge_type(MOIB.bridge_type(b, S), S)
 end
+
+"""
+   unbridged_map(bridge::MOI.Bridges.Variable.AbstractBridge,
+                 vi::MOI.VariableIndex)
+
+For a bridged variable in a scalar set, return a tuple of pairs mapping the
+variables created by the bridge to an affine expression in terms of the
+bridged variable `vi`.
+
+   unbridged_map(bridge::MOI.Bridges.Variable.AbstractBridge,
+                 vi::MOI.VariableIndex, i::IndexInVector)
+
+For a bridged variable in a vector set, return a tuple of pairs mapping the
+variables created by the bridge to an affine expression in terms of the bridged
+variable `vi` corresponding to the `i`th variable of the vector.
+
+If there is no way to recover the expression in terms of the bridged variable
+`vi`, return `nothing`. See [`ZerosBridge`](@ref) for an example of bridge
+returning `nothing`.
+"""
+function unbridged_map end