/*
Euler problem 25
"""
The Fibonacci sequence is defined by the recurrence relation:
Fn = Fn−1 + Fn−2, where F1 = 1 and F2 = 1.
Hence the first 12 terms will be:
F1 = 1
F2 = 1
F3 = 2
F4 = 3
F5 = 5
F6 = 8
F7 = 13
F8 = 21
F9 = 34
F10 = 55
F11 = 89
F12 = 144
The 12th term, F12, is the first term to contain three digits.
What is the first term in the Fibonacci sequence to contain 1000 digits?
"""
This Pop-11 program was created by Hakan Kjellerstrand (hakank@bonetmail.com).
See also my Pop-11 / Poplog page: http://www.hakank.org/poplog/
*/
compile('/home/hakank/Poplib/init.p');
define fib(n);
if n <= 2 then
1
else
fib(n-1)+fib(n-2);
endif;
enddefine;
define problem25;
;;; Memoize the function
newmemo(fib, 20) -> fib;
lvars len = 0;
lvars f = 0;
while fib(f).unpackitem.length < 1000 do
f+1->f;
endwhile;
f=>;
enddefine;
'problem25()'=>
problem25();