# Template:Prelude/pow mod.a68

From Rosetta Code

COMMENT This routine is used in more than one place, and is essentially a template that can by used for many different types, eg INT, LONG INT... USAGE MODE POWMODSTRUCT = INT, LONG INT, COMPL, FRAC, MODULAS, MATRIX etc PR READ "prelude/pow_mod.a68" PR END COMMENT

PROC pow mod = (POWMODSTRUCT b,in e, mod)POWMODSTRUCT: ( POWMODSTRUCT sq := b, e := in e; POWMODSTRUCT out:= IF ODD e THEN b ELSE 1 FI; e:=e OVER 2; WHILE e /= 0 DO sq := sq * sq %* mod; IF ODD e THEN out := out * sq %* mod FI ; e:=e OVER 2 OD; out )