(phixonline)-->
with javascript_semantics
include mpfr.e
procedure mpz_mod_exp(mpz base, exponent, modulus, result)
if mpz_cmp_si(exponent,1)=0 then
mpz_set(result,base)
else
mpz _exp = mpz_init_set(exponent) -- (use a copy)
bool odd = mpz_odd(_exp)
if odd then
mpz_sub_ui(_exp,_exp,1)
end if
mpz_fdiv_q_2exp(_exp,_exp,1)
mpz_mod_exp(base,_exp,modulus,result)
_exp = mpz_free(_exp)
mpz_mul(result,result,result)
if odd then
mpz_mul(result,result,base)
end if
end if
mpz_mod(result,result,modulus)
end procedure
mpz base = mpz_init("2988348162058574136915891421498819466320163312926952423791023078876139"),
exponent = mpz_init("2351399303373464486466122544523690094744975233415544072992656881240319"),
modulus = mpz_init("1"&repeat('0',40)),
result = mpz_init()
mpz_mod_exp(base,exponent,modulus,result)
?mpz_get_str(result)
-- check against the builtin:
mpz_powm(result,base,exponent,modulus)
?mpz_get_str(result)