# 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 ] def

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

[ even? ] filter

\ns ::
    ns [ [+] doin ]
    ns length 1 - times

unquote println