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# This file is a part of Julia. License is MIT: http://julialang.org/license
isempty(itr) = done(itr, start(itr))
# enumerate
immutable Enumerate{I}
itr::I
end
enumerate(itr) = Enumerate(itr)
length(e::Enumerate) = length(e.itr)
start(e::Enumerate) = (1, start(e.itr))
function next(e::Enumerate, state)
n = next(e.itr,state[2])
(state[1],n[1]), (state[1]+1,n[2])
end
done(e::Enumerate, state) = done(e.itr, state[2])
eltype{I}(::Type{Enumerate{I}}) = Tuple{Int, eltype(I)}
# zip
abstract AbstractZipIterator
immutable Zip2{I1, I2} <: AbstractZipIterator
a::I1
b::I2
end
zip(a) = a
zip(a, b) = Zip2(a, b)
length(z::Zip2) = min(length(z.a), length(z.b))
eltype{I1,I2}(::Type{Zip2{I1,I2}}) = Tuple{eltype(I1), eltype(I2)}
start(z::Zip2) = (start(z.a), start(z.b))
function next(z::Zip2, st)
n1 = next(z.a,st[1])
n2 = next(z.b,st[2])
return ((n1[1], n2[1]), (n1[2], n2[2]))
end
done(z::Zip2, st) = done(z.a,st[1]) | done(z.b,st[2])
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))
@generated function tuple_type_cons{S,T<:Tuple}(::Type{S}, ::Type{T})
Tuple{S, T.parameters...}
end
eltype{I,Z}(::Type{Zip{I,Z}}) = tuple_type_cons(eltype(I), eltype(Z))
start(z::Zip) = tuple(start(z.a), start(z.z))
function next(z::Zip, st)
n1 = next(z.a, st[1])
n2 = next(z.z, st[2])
(tuple(n1[1], n2[1]...), (n1[2], n2[2]))
end
done(z::Zip, st) = done(z.a,st[1]) | done(z.z,st[2])
# filter
immutable Filter{F,I}
flt::F
itr::I
end
filter(flt, itr) = Filter(flt, itr)
start(f::Filter) = start_filter(f.flt, f.itr)
function start_filter(pred, itr)
s = start(itr)
while !done(itr,s)
v,t = next(itr,s)
if pred(v)
return (false, v, t)
end
s=t
end
(true,)
end
next(f::Filter, s) = advance_filter(f.flt, f.itr, s)
function advance_filter(pred, itr, st)
_, v, s = st
while !done(itr,s)
w,t = next(itr,s)
if pred(w)
return v, (false, w, t)
end
s=t
end
v, (true,)
end
done(f::Filter, s) = s[1]
eltype{I}(::Type{Filter{I}}) = eltype(I)
# Rest -- iterate starting at the given state
immutable Rest{I,S}
itr::I
st::S
end
rest(itr,state) = Rest(itr,state)
start(i::Rest) = i.st
next(i::Rest, st) = next(i.itr, st)
done(i::Rest, st) = done(i.itr, st)
eltype{I}(::Type{Rest{I}}) = eltype(I)
# Count -- infinite counting
immutable Count{S<:Number}
start::S
step::S
end
countfrom(start::Number, step::Number) = Count(promote(start, step)...)
countfrom(start::Number) = Count(start, one(start))
countfrom() = Count(1, 1)
eltype{S}(::Type{Count{S}}) = S
start(it::Count) = it.start
next(it::Count, state) = (state, state + it.step)
done(it::Count, state) = false
# Take -- iterate through the first n elements
immutable Take{I}
xs::I
n::Int
end
take(xs, n::Int) = Take(xs, n)
eltype{I}(::Type{Take{I}}) = eltype(I)
start(it::Take) = (it.n, start(it.xs))
function next(it::Take, state)
n, xs_state = state
v, xs_state = next(it.xs, xs_state)
return v, (n - 1, xs_state)
end
function done(it::Take, state)
n, xs_state = state
return n <= 0 || done(it.xs, xs_state)
end
# Drop -- iterator through all but the first n elements
immutable Drop{I}
xs::I
n::Int
end
drop(xs, n::Int) = Drop(xs, n)
eltype{I}(::Type{Drop{I}}) = eltype(I)
function start(it::Drop)
xs_state = start(it.xs)
for i in 1:it.n
if done(it.xs, xs_state)
break
end
_, xs_state = next(it.xs, xs_state)
end
xs_state
end
next(it::Drop, state) = next(it.xs, state)
done(it::Drop, state) = done(it.xs, state)
# Cycle an iterator forever
immutable Cycle{I}
xs::I
end
cycle(xs) = Cycle(xs)
eltype{I}(::Type{Cycle{I}}) = eltype(I)
function start(it::Cycle)
s = start(it.xs)
return s, done(it.xs, s)
end
function next(it::Cycle, state)
s, d = state
if done(it.xs, s)
s = start(it.xs)
end
v, s = next(it.xs, s)
return v, (s, false)
end
done(it::Cycle, state) = state[2]
# Repeat an object infinitely many times
immutable Repeated{O}
x::O
end
repeated(x) = Repeated(x)
eltype{O}(::Type{Repeated{O}}) = O
start(it::Repeated) = nothing
next(it::Repeated, state) = (it.x, nothing)
done(it::Repeated, state) = false
repeated(x, n::Int) = take(repeated(x), n)
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