Use function objects instead of symbols

Author: HarrisonGrodin

src/simplify.jl

@@ -4,35 +4,35 @@ function simplify_constants(O::Operation,shorten_tree = true)
     while _O != O_last
         O_last = _O
         _O = _simplify_constants(_O,shorten_tree)
-        if typeof(_O) <: Operation
+        if is_operation(_O)
             _O = Operation(_O.op,simplify_constants.(_O.args,shorten_tree))
         end
     end
     _O
 end
 
-const TREE_SHRINK_OPS = [:*,:+]
+const TREE_SHRINK_OPS = [*, +]
 
 function _simplify_constants(O,shorten_tree = true)
     # Tree shrinking
     if shorten_tree
       for cur_op in TREE_SHRINK_OPS
-        if Symbol(O.op) == cur_op
+        if O.op == cur_op
           # Shrink tree
-          if any(x->typeof(x)<:Operation && Symbol(x.op) == cur_op ,O.args)
-              idxs = findall(x->typeof(x)<:Operation && Symbol(x.op) == cur_op,O.args)
+          if any(x -> is_operation(x) && x.op == cur_op, O.args)
+              idxs = findall(x -> is_operation(x) && x.op == cur_op, O.args)
               keep_idxs = 1:length(O.args) .∉ (idxs,)
               args = Vector{Expression}[O.args[i].args for i in idxs]
               push!(args,O.args[keep_idxs])
-              return Operation(O.op,vcat(args...))
+              return Operation(O.op, vcat(args...))
           end
           # Collapse constants
           idxs = findall(is_constant, O.args)
           if length(idxs) > 1
               other_idxs = 1:length(O.args) .∉ (idxs,)
-              if cur_op == :*
+              if cur_op == (*)
                 new_var = Constant(prod(get, O.args[idxs]))
-              elseif cur_op == :+
+              elseif cur_op == (+)
                 new_var = Constant(sum(get, O.args[idxs]))
               end
               new_args = O.args[other_idxs]
@@ -47,7 +47,7 @@ function _simplify_constants(O,shorten_tree = true)
       end
     end
 
-    if Symbol(O.op) == :*
+    if O.op == (*)
         # If any variable is `Constant(0)`, zero the whole thing
         # If any variable is `Constant(1)`, remove that `Constant(1)` unless
         # they are all `Constant(1)`, in which case simplify to a single variable
@@ -66,7 +66,7 @@ function _simplify_constants(O,shorten_tree = true)
         else
             return O
         end
-    elseif Symbol(O.op) == :+ && any(iszero, O.args)
+    elseif O.op == (+) && any(iszero, O.args)
         # If there are Constant(0)s in a big `+` expression, get rid of them
         idxs = findall(iszero, O.args)
         _O = Operation(O.op,O.args[1:length(O.args) .∉ (idxs,)])
@@ -79,7 +79,7 @@ function _simplify_constants(O,shorten_tree = true)
         end
     elseif O.op == identity
         return O.args[1]
-    elseif Symbol(O.op) == :- && length(O.args) == 1
+    elseif O.op == (-) && length(O.args) == 1
         return Operation(*,Expression[-1,O.args[1]])
     else
         return O

src/utils.jl

@@ -21,3 +21,6 @@ toexpr(ex) = MacroTools.postwalk(x->x isa Union{Expression,Operation} ? Expr(x)
 
 is_constant(x::Variable) = x.subtype === :Constant
 is_constant(::Any) = false
+
+is_operation(::Operation) = true
+is_operation(::Any) = false