# By considering the terms in the Fibonacci sequence whose values do not
# exceed four million, find the sum of the even-valued terms.
# https://projecteuler.net/problem=2

[1 2]

[[a b] : a b a b +] [fib-once] def

4 1000 * 1000 * \4_million ->

[dup last 4_million gt?] [[fib-once] doin] while

[even?] filter

[ns] =>
    ns [[+] doin]
    ns length 1 - times

unquote println