Add IsIterable trait (#25)

Add IsIterable trait

Author: davidanthoff

src/base-traits.jl

@@ -4,7 +4,7 @@ using SimpleTraits
 using Compat
 
 export IsLeafType, IsBits, IsImmutable, IsContiguous, IsIndexLinear,
-       IsAnything, IsNothing, IsCallable
+       IsAnything, IsNothing, IsCallable, IsIterable
 
 "Trait which contains all types"
 @traitdef IsAnything{X}
@@ -57,4 +57,10 @@ end
 
 Base.@deprecate_binding IsFastLinearIndex IsIndexLinear
 
+"Trait of all iterable types"
+@traitdef IsIterable{X}
+@generated function SimpleTraits.trait{X}(::Type{IsIterable{X}})
+    method_exists(start, Tuple{X}) ? :(IsIterable{X}) : :(Not{IsIterable{X}})
+end
+
 end # module

test/base-traits.jl

@@ -30,3 +30,8 @@ if VERSION < v"0.5.0-dev"
     # this give deprecation warning in Julia 0.5
     @test istrait(IsCallable{Base.AddFun})
 end
+
+@test istrait(IsIterable{Array})
+@test !istrait(IsIterable{Cmd})
+@test istrait(IsIterable{Base.UnitRange{Int}})
+@test istrait(IsIterable{Base.UnitRange})