use substitute function from SymbolicUtils

Author: shashi

Project.toml

@@ -37,7 +37,7 @@ NaNMath = "0.3"
 SafeTestsets = "0.0.1"
 SpecialFunctions = "0.7, 0.8, 0.9, 0.10"
 StaticArrays = "0.10, 0.11, 0.12"
-SymbolicUtils = "0.1.1, 0.2"
+SymbolicUtils = "0.2.1, 0.2"
 TreeViews = "0.3"
 UnPack = "0.1"
 Unitful = "1.1"

src/utils.jl

@@ -116,8 +116,7 @@ function _substitute(expr, ks, vs)
 end
 
 function _substitute(expr, dict::Dict)
-    sub = SymbolicUtils.RuleSet([SymbolicUtils.@rule(~x::(x->haskey(dict, x)) => dict[~x])])
-    to_mtk(simplify(sub(expr)))
+    to_mtk(simplify(SymbolicUtils.substitute(expr, dict)))
 end
 
 @deprecate substitute_expr!(expr,s) substitute(expr,s)