22 lines
546 B
Rexx
22 lines
546 B
Rexx
/* Modular exponentiation */
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numeric digits 100
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say powerMod(,
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2988348162058574136915891421498819466320163312926952423791023078876139,,
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2351399303373464486466122544523690094744975233415544072992656881240319,,
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1e40)
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exit
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powerMod: procedure
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parse arg base, exponent, modulus
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exponent = strip(x2b(d2x(exponent)), 'L', '0')
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result = 1
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base = base // modulus
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do exponentPos=length(exponent) to 1 by -1
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if substr(exponent, exponentPos, 1) = '1'
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then result = (result * base) // modulus
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base = (base * base) // modulus
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end
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return result
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