assume simplify always returns Expression

Author: shashi

src/differentials.jl

@@ -52,7 +52,7 @@ function expand_derivatives(O::Operation)
         end |> simplify_constants
     end
 
-    return O |> simplify_constants
+    return simplify_constants(O)
 end
 expand_derivatives(x) = x
 

src/direct.jl

@@ -50,7 +50,6 @@ function simplified_expr(O::Operation)
 end
 
 simplified_expr(c::Constant) = c.value
-simplified_expr(c) = c
 
 function simplified_expr(eq::Equation)
     Expr(:(=), simplified_expr(eq.lhs), simplified_expr(eq.rhs))

src/systems/abstractsystem.jl

@@ -216,4 +216,4 @@ function (f::AbstractSysToExpr)(O::Operation)
     end
     return build_expr(:call, Any[O.op; f.(O.args)])
 end
-(f::AbstractSysToExpr)(x) = to_Expr(x)
+(f::AbstractSysToExpr)(x) = convert(Expr, x)

src/systems/diffeqs/abstractodesystem.jl

@@ -34,7 +34,7 @@ function (f::ODEToExpr)(O::Operation)
     end
     return build_expr(:call, Any[Symbol(O.op); f.(O.args)])
 end
-(f::ODEToExpr)(x) = to_Expr(x)
+(f::ODEToExpr)(x) = convert(Expr, x)
 
 function generate_tgrad(sys::AbstractODESystem, dvs = states(sys), ps = parameters(sys); kwargs...)
     tgrad = calculate_tgrad(sys)

src/utils.jl

@@ -114,6 +114,3 @@ function substitute_expr!(expr::Operation, s::Pair{Operation, Operation})
     end
     return nothing
 end
-
-to_Expr(x::Expression) = convert(Expr, x)
-to_Expr(x::Number) = to_Expr(Constant(x))