RosettaCodeData/Task/Modular-exponentiation/ALGOL-68/modular-exponentiation.alg

24 lines
734 B
Plaintext

BEGIN
PR precision=1000 PR
MODE LLI = LONG LONG INT; CO For brevity CO
PROC mod power = (LLI base, exponent, modulus) LLI :
BEGIN
LLI result := 1, b := base, e := exponent;
IF exponent < 0
THEN
put (stand error, (("Negative exponent", exponent, newline)))
ELSE
WHILE e > 0
DO
(ODD e | result := (result * b) MOD modulus);
e OVERAB 2; b := (b * b) MOD modulus
OD
FI;
result
END;
LLI a = 2988348162058574136915891421498819466320163312926952423791023078876139;
LLI b = 2351399303373464486466122544523690094744975233415544072992656881240319;
LLI m = 10000000000000000000000000000000000000000;
printf (($"Last 40 digits = ", 40dl$, mod power (a, b, m)))
END