Remainder is probably the one you want. Robby
On Thursday, October 14, 2010, Joe Marshall <jmarsh...@alum.mit.edu> wrote: > Here's an interesting data point. > > (define (first-digit-fast-1 n) > (if (> 10 n) > n > (let loop ((i 10) > (next 100)) > (if (> next n) > (first-digit-fast (floor (/ n i))) > (loop next (* i i)))))) > > This takes about 13 seconds on my work machine. > > If I take advantage of the types: > > (define (first-digit-fast-2 n) > (if (and (fixnum? n) > (fix:> 10 n)) > n > (let loop ((i 10) > (next 100)) > (if (int:> next n) > (first-digit-fast (int:quotient n i)) > (loop next (int:* i i)))))) > > This takes about 3 seconds. > > I think the culprit is the call to (floor (/ n i)) > The division will allocate an unnecessary rational. The int:quotient > primitive doesn't need to. > > I'm pretty sure that Racket has some similar primitives. > > -- > ~jrm > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
