1. I would hope that some generics might help here. 2. I see a need for struct mixins here because meter isn't a refinement per se but some 'attribute'. Then you could mixin several different units and I may have both m and m-1.
Data representation not fully thought thru. -- Matthias On Oct 26, 2013, at 11:26 AM, Laurent wrote: > How would you represents quantities like 2 kg.m^2/s^-2 with that? > And how would you convert from mi/h to m/s? > > Anyway, I've started adding in some converters: > https://github.com/Metaxal/measures/blob/master/converters.rkt > > Some more to come, but I may not be able to work on it for very long for now. > > Laurent > > > On Sat, Oct 26, 2013 at 5:05 PM, Matthias Felleisen <matth...@ccs.neu.edu> > wrote: > > > Wouldn't we want something like this: > > #lang racket > > (module+ test (require rackunit)) > > (struct distance (value) #:transparent) ;; this should be abstract > (struct yard distance () #:transparent) > (struct meter distance () #:transparent) > > ;; distance distance -> distance > > (module+ test > (check-equal? (d+ (yard 1) (yard 2)) (yard 3)) > (check-equal? (d+ (yard 1) (meter 2)) (meter (+ .9 2))) > (check-equal? (d+ (meter 1.8) (yard 1)) (yard (+ 2.0 1))) > (check-equal? (d+ (meter 2) (meter 1)) (meter 3))) > > (define (d+ d1 d2) > (match (list d1 d2) > [(list (struct yard (value)) (struct yard (value2))) (yard (+ value > value2))] > [(list (struct yard (value)) (struct meter (value2))) (meter (+ > (yard->meter value) value2))] > [(list (struct meter (value2)) (struct yard (value))) (yard (+ > (meter->yard value2) value))] > [(list (struct meter (value)) (struct meter (value2))) (meter (+ value > value2))])) > > ;; distance distance-constructor -> distance > > (module+ test > (check-equal? (conversion (yard 3) meter) (meter (* 3 .9)))) > > (define (conversion x d) > (match x > [(struct yard (y)) (if (eq? yard d) x (meter (yard->meter y)))] > [(struct meter (y)) (if (eq? yard d) (yard (meter->yard y)) x)])) > > > ;; auxiliaries > (define (yard->meter v) (* .9 v)) > (define (meter->yard v) (/ v .9)) > > -- Matthias > > > > On Oct 26, 2013, at 7:20 AM, Laurent wrote: > >> Ok, so I just hacked together a small lib for handling numbers with unit >> symbols and exponents: >> >> Quick example: >> > (measure->value >> (m* '(18 s) >> '(1600 km (h -1)) >> '(1000 m (km -1)) >> '(1/3600 h (s -1)))) >> '(8000 m) >> >> You can get it with: >> $ raco pkg install measures >> or from the File menu in DrRacket, if you have a recent version of Racket >> (strictly > 5.3.6). >> >> Examples and details here: >> https://github.com/Metaxal/measures >> >> HTH, >> Laurent >> >> >> On Fri, Oct 25, 2013 at 12:51 AM, Alvin Schatte <alvinscha...@skytex.net> >> wrote: >> Is there a library or package that combines numbers and their operations >> with dimensions that may be associated with them? >> Alvin Schatte >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users >> >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users > >
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