clean up Switch in split-sign constraints, also equal_value_constraint

src/builders/compare.jl

@@ -29,7 +29,7 @@ $(TYPEDSIGNATURES)
 
 A constraint that makes sure that the values of `a` and `b` are the same.
 """
-same_value_constraint(a, b) = difference_constraint(a, b, 0)
+equal_value_constraint(a, b) = difference_constraint(a, b, 0)
 
 """
 $(TYPEDSIGNATURES)
@@ -39,9 +39,9 @@ value of `a`.
 
 Names in the output `ConstraintTree` match the names in the `tree`.
 """
-all_same_constraints(a, tree::C.ConstraintTree) =
+all_equal_constraints(a, tree::C.ConstraintTree) =
     C.map(tree) do b
-        same_value_constraint(a, b)
+        equal_value_constraint(a, b)
     end
 
 """

src/builders/unsigned.jl

@@ -32,7 +32,7 @@ sign_split_constraints(;
     signed::C.ConstraintTree,
 ) =
     C.zip(positive, negative, signed, C.Constraint) do p, n, s
-        C.Constraint(s.value + n.value - p.value, 0.0)
+        equal_value_constraint(s.value + n.value, p.value, 0.0)
     end
 #TODO the construction needs an example in the docs.
 
@@ -43,7 +43,10 @@ positive_bound_contribution(b::C.Between) =
     b.lower >= 0 && b.upper >= 0 ? b :
     b.lower <= 0 && b.upper <= 0 ? C.EqualTo(0) :
     C.Between(max(0, b.lower), max(0, b.upper))
-# TODO binary doesn't really fit here but it would be great if it could.
+positive_bound_contribution(b::C.Switch) =
+    let upper_bound = max(b.a, b.b)
+        upper_bound > 0 ? C.Between(0.0, upper_bound) : C.EqualTo(0.0)
+    end
 
 unsigned_positive_contribution_variables(cs::C.ConstraintTree) =
     C.variables_for(c -> positive_bound_contribution(c.bound), cs)

src/solver.jl

@@ -25,9 +25,15 @@ variable, and the value is constrained to equal `a + boolean_var * (b-a)`.
 Switches can be offset by adding real numbers, negated, and multiplied and
 divided by scalar constraints. For optimizing some special cases, multiplying
 by exact zero returns an equality bound to zero.
+
+# Fields
+$(TYPEDFIELDS)
 """
-struct Switch <: C.Bound
+Base.@kwdef mutable struct Switch
+    "One choice"
     a::Float64
+
+    "The other choice"
     b::Float64
 end