This commit is contained in:
Ingy döt Net 2013-04-10 21:29:02 -07:00
parent 764da6cbbb
commit db842d013d
19005 changed files with 197040 additions and 7 deletions

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package require Tcl 8.5
# Algorithm from http://introcs.cs.princeton.edu/java/78crypto/ModExp.java.html
# but Tcl has arbitrary-width integers and an exponentiation operator, which
# helps simplify the code.
proc tcl::mathfunc::modexp {a b n} {
if {$b == 0} {return 1}
set c [expr {modexp($a, $b / 2, $n)**2 % $n}]
if {$b & 1} {
set c [expr {($c * $a) % $n}]
}
return $c
}

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set a 2988348162058574136915891421498819466320163312926952423791023078876139
set b 2351399303373464486466122544523690094744975233415544072992656881240319
set n [expr {10**40}]
puts [expr {modexp($a,$b,$n)}]

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package require Tcl 8.5
proc modexp {a b n} {
for {set c 1} {$b} {set a [expr {$a*$a % $n}]} {
if {$b & 1} {
set c [expr {$c*$a % $n}]
}
set b [expr {$b >> 1}]
}
return $c
}

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set a 2988348162058574136915891421498819466320163312926952423791023078876139
set b 2351399303373464486466122544523690094744975233415544072992656881240319
set n [expr {10**40}]
puts [modexp $a $b $n]