How about `(hash-set #hash() k v)`? (I probably should have been more careful in defining `hash` to allow it to return a constant when given 0 arguments.)
At Sat, 28 Jun 2014 09:56:05 -0400 (EDT), "J. Ian Johnson" wrote: > I depend highly on creating singleton hashes in my program (one key maps). I > tried a few ways to create them, but alas directly using hash is the best. TR > can't type non-nullary applications hash though. > The times of the following test are the same in TR as in normal Racket, so > I'd > like to see peephole optimizations that turn the first two into the last one: > > #lang racket > > (define N 5000000) > (define keys (build-list N (λ (d) (random)))) > (define values (build-list N (λ (d) (random)))) > > (define (clean!) > (collect-garbage) > (collect-garbage) > (collect-garbage)) > (clean!) > (time (for ([k (in-list keys)] > [v (in-list values)]) > (hash-set (hash) k v))) > ;cpu time: 460 real time: 461 gc time: 13 > > (clean!) > (time (for ([k (in-list keys)] > [v (in-list values)]) > (make-immutable-hash (list (cons k v))))) > ;cpu time: 507 real time: 506 gc time: 29 > > (clean!) > (time (for ([k (in-list keys)] > [v (in-list values)]) > (hash k v))) > ;cpu time: 393 real time: 392 gc time: 17 > > ;;;;;;;;;;; > > I'd provide a patch, but I don't know where this kind of thing lives in the > compiler if it exists at all. > -Ian > > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev _________________________ Racket Developers list: http://lists.racket-lang.org/dev
