Merge pull request #156 from JuliaSymbolics/myb/int

Use _isinteger check in power rules

Author: shashi

Project.toml

@@ -1,7 +1,7 @@
 name = "SymbolicUtils"
 uuid = "d1185830-fcd6-423d-90d6-eec64667417b"
 authors = ["Shashi Gowda"]
-version = "0.6.2"
+version = "0.6.3"
 
 [deps]
 AbstractAlgebra = "c3fe647b-3220-5bb0-a1ea-a7954cac585d"

src/simplify_rules.jl

@@ -35,8 +35,8 @@ let
 
 
     POW_RULES = [
-        @rule(^(*(~~x), ~y::isliteral(Integer)) => *(map(a->pow(a, ~y), ~~x)...))
-        @rule((((~x)^(~p::isliteral(Integer)))^(~q::isliteral(Integer))) => (~x)^((~p)*(~q)))
+        @rule(^(*(~~x), ~y::_isinteger) => *(map(a->pow(a, ~y), ~~x)...))
+        @rule((((~x)^(~p::_isinteger))^(~q::_isinteger)) => (~x)^((~p)*(~q)))
         @rule(^(~x, ~z::_iszero) => 1)
         @rule(^(~x, ~z::_isone) => ~x)
         @rule(inv(~x) => ~x ^ -1)

src/utils.jl

@@ -111,10 +111,10 @@ is_operation(f) = @nospecialize(x) -> istree(x) && (operation(x) == f)
 isliteral(::Type{T}) where {T} = x -> x isa T
 is_literal_number(x) = isliteral(Number)(x)
 
-_iszero(t) = false
-_iszero(x::Number) = iszero(x)
-_isone(t) = false
-_isone(x::Number) = isone(x)
+# checking the type directly is faster than dynamic dispatch in type unstable code
+_iszero(x) = x isa Number && iszero(x)
+_isone(x) = x isa Number && isone(x)
+_isinteger(x) = (x isa Number && isinteger(x)) || (x isa Symbolic && symtype(x) <: Integer)
 
 issortedₑ(args) = issorted(args, lt=<ₑ)
 needs_sorting(f) = x -> is_operation(f)(x) && !issortedₑ(arguments(x))

test/rulesets.jl

@@ -38,6 +38,7 @@ end
     @eqtest simplify(a + b + 0*c + d) == simplify(a + b + d)
     @eqtest simplify(a * b * c^0 * d) == simplify(a * b * d)
     @eqtest simplify(a * b * 1*c * d) == simplify(a * b * c * d)
+    @eqtest simplify(x^2.0/(x*y)^2.0) == y ^ (-2.0)
 
     @test simplify(Term(one, [a])) == 1
     @test simplify(Term(one, [b+1])) == 1