Julia 0.7-DEV の新しい Iteration に触れてみた。 ref: https://qiita.com/antimon2/items/8b1a96d1370bb6252757

file0.txt

for cw in Zundoko()
    print(cw)
end

file1.txt

iter = Zundoko()
state = start(iter)
while !done(iter, state)
    (cw, state) = next(iter, state)
    print(cw)
end

file2.txt

iter = Zundoko()
_next = iterate(iter)
while _next !== nothing
    (cw, state) = _next
    print(cw)
    _next = iterate(iter, state)
end

file3.txt

for line in iter
    println(line)
end

file4.txt

_next = iterate(iter)
while _next !== nothing
    (line, state) = _next
    println(line)
    _next = iterate(iter, state)
end

file5.txt

state = start(iter)
while !done(iter, state)
    (line, state) = next(iter, state)
    println(line)
end

zundoko_iter_v06.jl

struct ZunDoko end

Base.start(::ZunDoko) = 0
Base.done(::ZunDoko, i::Int) = i == 6
function Base.next(::ZunDoko, i::Int)
    if i == 5
        ("キ・ヨ・シ！", 6)
    elseif i == 4
        rand([("ズン", 4), ("ドコ", 5)])
    else
        rand([("ズン", i + 1), ("ドコ", 0)])
    end
end

zundoko_iter_v07.jl

struct ZunDoko end

function Base.iterate(::ZunDoko, i::Int = 0)
    i == 6 && return nothing
    if i == 5
        ("キ・ヨ・シ！", 6)
    elseif i == 4
        rand([("ズン", 4), ("ドコ", 5)])
    else
        rand([("ズン", i + 1), ("ドコ", 0)])
    end
end