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zips, products and takes with infinite components #15400

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Mar 11, 2016
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zips, products and takes with infinite components #15400

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01dc9fb
zips, products and takes with infinite components
mschauer Mar 8, 2016
3b34120
length() of Take and Drop iterators
mschauer Mar 10, 2016
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40 changes: 33 additions & 7 deletions base/iterator.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,16 @@

isempty(itr) = done(itr, start(itr))

_min_length(a, b, ::IsInfinite, ::IsInfinite) = min(length(a),length(b)) # inherit behaviour, error
_min_length(a, b, A, ::IsInfinite) = length(a)
_min_length(a, b, ::IsInfinite, B) = length(b)
_min_length(a, b, A, B) = min(length(a),length(b))

_diff_length(a, b, A, ::IsInfinite) = 0
_diff_length(a, b, ::IsInfinite, ::IsInfinite) = 0
_diff_length(a, b, ::IsInfinite, B) = length(a) # inherit behaviour, error
_diff_length(a, b, A, B) = max(length(a)-length(b), 0)

# enumerate

immutable Enumerate{I}
Expand All @@ -27,6 +37,12 @@ iteratoreltype{I}(::Type{Enumerate{I}}) = iteratoreltype(I)

abstract AbstractZipIterator

zip_iteratorsize(a, b) = and_iteratorsize(a,b) # as `and_iteratorsize` but inherit `Union{HasLength,IsInfinite}` of the shorter iterator
zip_iteratorsize(::HasLength, ::IsInfinite) = HasLength()
zip_iteratorsize(::HasShape, ::IsInfinite) = HasLength()
zip_iteratorsize(a::IsInfinite, b) = zip_iteratorsize(b,a)


immutable Zip1{I} <: AbstractZipIterator
a::I
end
Expand All @@ -49,7 +65,7 @@ immutable Zip2{I1, I2} <: AbstractZipIterator
b::I2
end
zip(a, b) = Zip2(a, b)
length(z::Zip2) = min(length(z.a), length(z.b))
length(z::Zip2) = _min_length(z.a, z.b, iteratorsize(z.a), iteratorsize(z.b))
size(z::Zip2) = promote_shape(size(z.a), size(z.b))
eltype{I1,I2}(::Type{Zip2{I1,I2}}) = Tuple{eltype(I1), eltype(I2)}
@inline start(z::Zip2) = (start(z.a), start(z.b))
Expand All @@ -60,15 +76,15 @@ eltype{I1,I2}(::Type{Zip2{I1,I2}}) = Tuple{eltype(I1), eltype(I2)}
end
@inline done(z::Zip2, st) = done(z.a,st[1]) | done(z.b,st[2])

iteratorsize{I1,I2}(::Type{Zip2{I1,I2}}) = and_iteratorsize(iteratorsize(I1),iteratorsize(I2))
iteratorsize{I1,I2}(::Type{Zip2{I1,I2}}) = zip_iteratorsize(iteratorsize(I1),iteratorsize(I2))
iteratoreltype{I1,I2}(::Type{Zip2{I1,I2}}) = and_iteratoreltype(iteratoreltype(I1),iteratoreltype(I2))

immutable Zip{I, Z<:AbstractZipIterator} <: AbstractZipIterator
a::I
z::Z
end
zip(a, b, c...) = Zip(a, zip(b, c...))
length(z::Zip) = min(length(z.a), length(z.z))
length(z::Zip) = _min_length(z.a, z.z, iteratorsize(z.a), iteratorsize(z.z))
size(z::Zip) = promote_shape(size(z.a), size(z.z))
tuple_type_cons{S}(::Type{S}, ::Type{Union{}}) = Union{}
function tuple_type_cons{S,T<:Tuple}(::Type{S}, ::Type{T})
Expand All @@ -84,7 +100,7 @@ eltype{I,Z}(::Type{Zip{I,Z}}) = tuple_type_cons(eltype(I), eltype(Z))
end
@inline done(z::Zip, st) = done(z.a,st[1]) | done(z.z,st[2])

iteratorsize{I1,I2}(::Type{Zip{I1,I2}}) = and_iteratorsize(iteratorsize(I1),iteratorsize(I2))
iteratorsize{I1,I2}(::Type{Zip{I1,I2}}) = zip_iteratorsize(iteratorsize(I1),iteratorsize(I2))
iteratoreltype{I1,I2}(::Type{Zip{I1,I2}}) = and_iteratoreltype(iteratoreltype(I1),iteratoreltype(I2))

# filter
Expand Down Expand Up @@ -141,7 +157,9 @@ done(i::Rest, st) = done(i.itr, st)

eltype{I}(::Type{Rest{I}}) = eltype(I)
iteratoreltype{I,S}(::Type{Rest{I,S}}) = iteratoreltype(I)
iteratorsize{T<:Rest}(::Type{T}) = SizeUnknown()
rest_iteratorsize(a) = SizeUnknown()
rest_iteratorsize(::IsInfinite) = IsInfinite()
iteratorsize{I,S}(::Type{Rest{I,S}}) = rest_iteratorsize(iteratorsize(I))

# Count -- infinite counting

Expand Down Expand Up @@ -171,7 +189,10 @@ take(xs, n::Int) = Take(xs, n)

eltype{I}(::Type{Take{I}}) = eltype(I)
iteratoreltype{I}(::Type{Take{I}}) = iteratoreltype(I)
iteratorsize{T<:Take}(::Type{T}) = SizeUnknown() # TODO
take_iteratorsize(a) = HasLength()
take_iteratorsize(::SizeUnknown) = SizeUnknown()
iteratorsize{I}(::Type{Take{I}}) = take_iteratorsize(iteratorsize(I))
length(t::Take) = _min_length(t.xs, 1:t.n, iteratorsize(t.xs), HasLength())

start(it::Take) = (it.n, start(it.xs))

Expand All @@ -196,7 +217,11 @@ drop(xs, n::Int) = Drop(xs, n)

eltype{I}(::Type{Drop{I}}) = eltype(I)
iteratoreltype{I}(::Type{Drop{I}}) = iteratoreltype(I)
iteratorsize{T<:Drop}(::Type{T}) = SizeUnknown() # TODO
drop_iteratorsize(::SizeUnknown) = SizeUnknown()
drop_iteratorsize(::Union{HasShape, HasLength}) = HasLength()
drop_iteratorsize(::IsInfinite) = IsInfinite()
iteratorsize{I}(::Type{Drop{I}}) = drop_iteratorsize(iteratorsize(I))
length(d::Drop) = _diff_length(d.xs, 1:d.n, iteratorsize(d.xs), HasLength())

function start(it::Drop)
xs_state = start(it.xs)
Expand Down Expand Up @@ -327,6 +352,7 @@ iteratorsize{I1,I2}(::Type{Prod{I1,I2}}) = prod_iteratorsize(iteratorsize(I1),it
end

prod_iteratorsize(::Union{HasLength,HasShape}, ::Union{HasLength,HasShape}) = HasLength()
prod_iteratorsize(a, ::IsInfinite) = IsInfinite() # products can have an infinite last iterator (which moves slowest)
prod_iteratorsize(a, b) = SizeUnknown()

_size(p::Prod2) = (length(p.a), length(p.b))
Expand Down
17 changes: 17 additions & 0 deletions test/functional.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -76,13 +76,20 @@ let zeb = IOBuffer("1\n2\n3\n4\n5\n"),
@test res == [(1, 'a'), (2, 'b'), (3, 'c'), (4, 'd'), (5, 'e')]
end

@test length(zip(cycle(1:3), 1:7)) == 7
@test length(zip(cycle(1:3), 1:7, cycle(1:3))) == 7
@test length(zip(1:3,Base.product(1:7,cycle(1:3)))) == 3
@test length(zip(1:3,Base.product(1:7,cycle(1:3)),8)) == 1

# rest
# ----
let s = "hello"
_, st = next(s, start(s))
@test collect(rest(s, st)) == ['e','l','l','o']
end

@test_throws MethodError collect(rest(countfrom(1), 5))

# countfrom
# ---------

Expand Down Expand Up @@ -115,6 +122,10 @@ let i = 0
@test i == 10
end

@test length(take(1:3,typemax(Int))) == 3
@test length(take(countfrom(1),3)) == 3
@test length(take(1:6,3)) == 3

# drop
# ----

Expand All @@ -126,6 +137,10 @@ let i = 0
@test i == 4
end

@test length(drop(1:3,typemax(Int))) == 0
@test Base.iteratorsize(drop(countfrom(1),3)) == Base.IsInfinite()
@test_throws MethodError length(drop(countfrom(1), 3))

# cycle
# -----

Expand Down Expand Up @@ -155,6 +170,7 @@ let i = 0
end
end


# product
# -------

Expand All @@ -165,6 +181,7 @@ end
@test collect(Base.product(1:2,3:4)) == [(1,3),(2,3),(1,4),(2,4)]
@test isempty(collect(Base.product(1:0,1:2)))
@test length(Base.product(1:2,1:10,4:6)) == 60
@test Base.iteratorsize(Base.product(1:2, countfrom(1))) == Base.IsInfinite()

# foreach
let
Expand Down