function source(c)
    for k = 1:100000
        put!(c, (1+k)*k÷2)
    end
end

function make_pairs(c, src)
    buffer = false
    for chunk in src
        if buffer == false
	    buffer = chunk
	else
	    put!(c, (buffer, chunk))
	    buffer = false
	end
    end
end

function split(c, src)
    for chunk in src
        put!(c, chunk)
	put!(c, chunk)
    end
end

function multiply(c, src)
    for (x, y) in src
        put!(c, x*y)
    end
end

function toy_gcd(c, src)
    function helper(x, y)
        if x < y
	    helper(y, x)
	elseif y == 0
	    put!(c, x)
	else
	    helper(y, x%y)
	end
    end
    for (x, y) in src
        helper(x, y)
    end
end

function combine(c, src1, src2)
    for x in src1
        put!(c, (x, take!(src2)))
    end
end

function divide(c, src)
    for (x, y) in src
        put!(c, x÷y)
    end
end

function get_digits(c, src)
    function helper(x)
        if x != 0
	    helper(x÷10)
	    put!(c, x%10)
	end
    end
    for x in src
    	helper(x)
    end
end

function sink(src)
    for chunk in src
    end
end

function pipe(func, src...)
    Channel(c -> func(c, src...))
end

function pipeline()
    s = pipe(split, pipe(make_pairs, Channel(source)))
    sink(pipe(get_digits, pipe(divide, pipe(combine, pipe(multiply, s), pipe(toy_gcd, s)))))
end

function repeat()
    for i = 1:100
        pipeline()
    end
end

println(@elapsed repeat())