length for chain (fixes #84)

src/Iterators.jl

@@ -28,7 +28,8 @@ if VERSION < v"0.5.0-dev+3305"
         error("Do not call this on older versions")
     end
 else
-    import Base: iteratorsize, SizeUnknown, IsInfinite, HasLength
+    import Base: iteratorsize, SizeUnknown, IsInfinite,
+                HasLength, HasShape
 end
 
 
@@ -105,17 +106,32 @@ done(it::RepeatCallForever, state) = false
 
 
 # Concatenate the output of n iterators
-
 immutable Chain{T<:Tuple}
     xss::T
 end
 
-iteratorsize{T<:Chain}(::Type{T}) = SizeUnknown()
+if VERSION >= v"0.5.0-dev+3305"
+    iteratorsize{T}(::Type{Chain{T}}) = _chain_is(T)
 
-eltype{T}(::Type{Chain{T}}) = typejoin([eltype(t) for t in T.parameters]...)
+    @generated function _chain_is{T}(t::Type{T})
+        for itype in T.types
+            if iteratorsize(itype) == IsInfinite()
+                return :(IsInfinite())
+            elseif iteratorsize(itype) == SizeUnknown()
+                return :(SizeUnknown())
+            end
+        end
+        return :(HasLength())
+    end
+end
 
 chain(xss...) = Chain(xss)
 
+length(it::Chain{Tuple{}}) = 0
+length(it::Chain) = sum(length, it.xss)
+
+eltype{T}(::Type{Chain{T}}) = typejoin([eltype(t) for t in T.parameters]...)
+
 function start(it::Chain)
     i = 1
     xs_state = nothing

test/runtests.jl

@@ -1,5 +1,9 @@
 using Iterators, Base.Test
 
+if VERSION >= v"0.5.0-dev+3305"
+	import Base: IsInfinite, SizeUnknown, HasLength, iteratorsize, HasShape
+end
+
 # count
 # -----
 
@@ -116,6 +120,53 @@ ch2 = chain(1:0, 1:2:5, 0.2:0.1:1.6)
 
 @test eltype(ch2) == typejoin(Int, Float64)
 @test collect(ch2) == [1:2:5; 0.2:0.1:1.6]
+@test length(ch2) == length(collect(ch2))
+if VERSION >= v"0.5.0-dev+3305"
+	@test iteratorsize(ch2) == HasLength()
+end
+
+ch3 = chain(1:10, 1:10, 1:10)
+@test length(ch3) == 30
+if VERSION >= v"0.5.0-dev+3305"
+	@test iteratorsize(ch3) == HasLength()
+end
+
+r = countfrom(1)
+ch4 = chain(1:10, countfrom(1))
+@test eltype(ch4) == Int
+@test_throws MethodError length(ch4)
+if VERSION >= v"0.5.0-dev+3305"
+	@assert iteratorsize(r) == IsInfinite()
+	@test iteratorsize(ch4) == IsInfinite()
+end
+
+ch5 = chain()
+@test length(ch5) == 0
+if VERSION >= v"0.5.0-dev+3305"
+	@test iteratorsize(ch5) == HasLength()
+end
+
+c = chain(ch1, ch2, ch3)
+@test length(c) == length(ch1) + length(ch2) + length(ch3)
+@test collect(c) == [collect(ch1); collect(ch2); collect(ch3)]
+
+r = rand(2,2)
+c = chain(r, r)
+@test length(c) == 8
+@test collect(c) == [vec(r); vec(r)]
+if VERSION >= v"0.5.0-dev+3305"
+	@test iteratorsize(r) == HasShape()
+	@test iteratorsize(c) == HasLength()
+end
+
+if VERSION >= v"0.5.0-dev+3305"
+	r = distinct(collect(1:10))
+	@test iteratorsize(r) == SizeUnknown() #lazy filtering
+	c = chain(1:10, r)
+	@test_throws MethodError length(c)
+	@test length(collect(c)) == 20
+	@test iteratorsize(c) == SizeUnknown()
+end
 
 # product
 # -------
@@ -557,4 +608,3 @@ end
 @test_chain [1,2,3] Any[] ['w', 'x', 'y', 'z']
 @test_chain [1,2,3] Union{}[] ['w', 'x', 'y', 'z']
 @test_chain [1,2,3] 4 [('w',3), ('x',2), ('y',1), ('z',0)]
-