Add tests

src/substitution.jl

@@ -24,13 +24,7 @@ is equivalent to:
 
     subs(polynomial, (x=>1, y=>2))
 """
-substitute(st::AST, p::APL, s::MultiSubstitution) = substitute(st, p, pairzip(s))
-
-# inefficient but convenient method to allow subs(p, (x, y)=>[1, 2])
-substitute(st::AST, p::APL, s::MultiVectorSubstitution) = substitute(st, p, s.first => Tuple(s.second))
-substitute(st::AST, p::APL, s::VectorMultiSubstitution) = substitute(st, p, Tuple(s.first) => s.second)
-substitute(st::AST, p::APL, s::VectorMultiVectorSubstitution) = substitute(st, p, Tuple(s.first) => Tuple(s.second))
-
+substitute(st::AST, p::APL, s::AbstractMultiSubstitution) = substitute(st, p, pairzip(s))
 
 # Evaluate the stream
 # If I do s2..., then

src/zip.jl

@@ -9,6 +9,8 @@ pairzip(::Tuple{}, ::Tuple) = throw(ArgumentError("args must be equal in length"
 pairzip(::Tuple, ::Tuple{}) = throw(ArgumentError("args must be equal in length"))
 pairzip(t::Tuple, u::Tuple) = (t[1] => u[1], pairzip(Base.tail(t), Base.tail(u))...)
 pairzip(p::Pair{<:Tuple, <:Tuple}) = pairzip(p.first, p.second)
+# inefficient but convenient method to allow subs(p, (x, y)=>[1, 2])
+pairzip(p::Pair) = pairzip(Tuple(p.first), Tuple(p.second))
 
 tuplezip(::Tuple{}, ::Tuple{}) = ()
 tuplezip(::Tuple{}, ::Tuple) = throw(ArgumentError("args must be equal in length"))

test/subs.jl

@@ -3,6 +3,10 @@ import Base.Test: @inferred
 @testset "Substitution" begin
     Mod.@polyvar x[1:3]
 
+    @test subs(2, x[1]=>3) == 2
+    @test iszero((x[1]-x[1])(x[1]=>x[2]))
+    @test subs(CustomPoly(x[1]+x[2]), x[2]=>x[1]) == 2x[1]
+
     a = (x[1])(x[1]=>x[2])
     b = x[2]
     @test (x[1])(x[1]=>x[2]) == x[2]