#!/usr/bin/env setl
--
-- Project Euler problem 21 in SETL
--
-- Problem 21
-- """
-- Let d(n) be defined as the sum of proper divisors of n (numbers less
-- than n which divide evenly into n).
-- If d(a) = b and d(b) = a, where a /= b, then a and b are an amicable
-- pair and each of a and b are called amicable numbers.
--
-- For example, the proper divisors of 220 are
-- 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110; therefore d(220) = 284.
-- The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.
--
-- Evaluate the sum of all the amicable numbers under 10000.
-- """
--
-- This SETL program was created by Hakan Kjellerstrand (hakank@bonetmail.com)
-- Also see my SETL page: http://www.hakank.org/setl/
--
-- This takes about 17 seconds
problem21();
proc divisors(n);
return [d : d in [1..1+fix(n/2)] | n mod d = 0];
end proc;
proc problem21;
nprint("Problem 21: ");
s := {};
for a in [1..10000-1] loop
b := +/divisors(a);
c := +/divisors(b);
if a /= b and a = c then
s +:= {a,b};
end if;
end loop;
print(+/s);
end proc;