Remove additional Variable methods in favor of Base.copy

Author: HarrisonGrodin

src/differentials.jl

@@ -12,12 +12,13 @@ function Derivative end
 function (D::Differential)(x::Variable)
     D.x === x             && return Constant(1)
     has_dependent(x, D.x) || return Constant(0)
-    return Variable(x,D)
+
+    x′ = copy(x)
+    x′.diff = D
+    return x′
 end
 Base.:(==)(D1::Differential, D2::Differential) = D1.order == D2.order && D1.x == D2.x
 
-Variable(x::Variable, D::Differential) = Variable(x.name, x.subtype, D, x.dependents)
-
 function expand_derivatives(O::Operation)
     @. O.args = expand_derivatives(O.args)
 

src/variables.jl

@@ -7,11 +7,7 @@ end
 
 Variable(name; subtype::Symbol=:Variable, dependents::Vector{Variable} = Variable[]) =
     Variable(name, subtype, nothing, dependents)
-Variable(name,args...;kwargs...) = Variable(name,args...;subtype=:Variable,kwargs...)
-
-Variable(name,x::Variable) = Variable(name,x.value_type,
-                x.subtype,D,x.dependents,x.description,x.flow,x.domain,
-                x.size,x.context)
+Variable(name, args...; kwargs...) = Variable(name, args...; subtype=:Variable, kwargs...)
 
 Parameter(name,args...;kwargs...) = Variable(name,args...;subtype=:Parameter,kwargs...)
 IndependentVariable(name,args...;kwargs...) = Variable(name,args...;subtype=:IndependentVariable,kwargs...)
@@ -45,6 +41,9 @@ export Variable,Parameter,Constant,DependentVariable,IndependentVariable,JumpVar
        @Var, @DVar, @IVar, @Param, @Const
 
 
+Base.copy(x::Variable) = Variable(x.name, x.subtype, x.diff, x.dependents)
+
+
 struct Constant <: Expression
     value::Number
 end