Merge pull request #100 from JuliaSymbolics/s/fold

propagate constants after substitute

Author: shashi

src/rule_dsl.jl

@@ -162,11 +162,12 @@ macro rule(expr)
     lhs_term = makepattern(lhs, keys)
     unique!(keys)
     quote
+        $(__source__)
         lhs_pattern = $(lhs_term)
         Rule($(QuoteNode(expr)),
              lhs_pattern,
              matcher(lhs_pattern),
-             (__MATCHES__, __CTX__) -> $(makeconsequent(rhs)),
+             (__MATCHES__, __CTX__) -> ($(__source__); $(makeconsequent(rhs))),
              rule_depth($lhs_term))
     end
 end

src/rulesets.jl

@@ -50,8 +50,8 @@ const TIMES_RULES = RuleSet([
 ])
 
 const POW_RULES = RuleSet([
-    @rule(^(*(~~x), ~y) => *(map(a->pow(a, ~y), ~~x)...))
-    @rule((((~x)^(~p))^(~q)) => (~x)^((~p)*(~q)))
+    @rule(^(*(~~x), ~y::isliteral(Integer)) => *(map(a->pow(a, ~y), ~~x)...))
+    @rule((((~x)^(~p::isliteral(Integer)))^(~q::isliteral(Integer))) => (~x)^((~p)*(~q)))
     @rule(^(~x, ~z::_iszero) => 1)
     @rule(^(~x, ~z::_isone) => ~x)
 ])

src/simplify.jl

@@ -57,7 +57,18 @@ substitute any subexpression that matches a key in `dict` with
 the corresponding value.
 """
 function substitute(expr, dict)
-    RuleSet([@rule ~x::(x->haskey(dict, x)) => dict[~x]])(expr)
+    RuleSet([@rule ~x::(x->haskey(dict, x)) => dict[~x]])(expr) |> fold
+end
+
+fold(x) = x
+function fold(t::Term)
+    tt = map(fold, arguments(t))
+    if !any(x->x isa Symbolic, tt)
+        # evaluate it
+        return operation(t)(tt...)
+    else
+        return Term{symtype(t)}(operation(t), tt)
+    end
 end
 
 ### Predicates

test/basics.jl

@@ -101,7 +101,8 @@ end
     @syms a b
     @test substitute(a, Dict(a=>1)) == 1
     @test isequal(substitute(sin(a+b), Dict(a=>1)), sin(1+b))
-    @test substitute(a+b, Dict(a=>1, b=>3)) |> simplify == 4
+    @test substitute(a+b, Dict(a=>1, b=>3)) == 4
+    @test substitute(exp(a), Dict(a=>2)) ≈ exp(2)
 end
 
 @testset "printing" begin

test/rulesets.jl

@@ -25,7 +25,8 @@ end
     @eqtest simplify(1 * x * 2) == 2 * x
     @eqtest simplify(1 + x + 2) == 3 + x
     @eqtest simplify(b*b) == b^2 # tests merge_repeats
-    @eqtest simplify((a*b)^c) == a^c * b^c
+    @eqtest simplify((a*b)^2) == a^2 * b^2
+    @eqtest simplify((a*b)^c) == (a*b)^c
 
     @eqtest simplify(1x + 2x) == 3x
     @eqtest simplify(3x + 2x) == 5x