Modular exponentiation: Difference between revisions

=={{header|Lambdatalk}}==

<lang scheme>

{require lib_BN}

{def power_mod

{lambda {:b :e :m :x}

{if {= {BN.compare :e 0} 1} // e > 0

then {power_mod {BN.% {BN.* :b :b} :m} // (b*b)%2

{BN.intPart {BN./ :e 2}} // e//2

:m

{if {= {BN.compare {BN.% :e 2} 0} 1} // e%2 > 0

then {BN.% {BN.* :b :x} :m} // (b*x)%m

else :x}}

else :x}}}

-> power_mod

{power_mod

2988348162058574136915891421498819466320163312926952423791023078876139

2351399303373464486466122544523690094744975233415544072992656881240319

{BN.pow 10 40} 1}

-> 1527229998585248450016808958343740453059 // 2900ms

</lang>