On Tuesday, November 15, 2016 at 5:30:54 PM UTC+1, Brian Adkins wrote: > I'm working on a simple chess engine in Racket as a learning exercise. I > initially wrote this function: > > (define (valid-queen-moves board idx is-opposite-color?) > (append (valid-bishop-moves board idx is-opposite-color?) > (valid-rook-moves board idx is-opposite-color?))) > > I didn't like the redundancy, so I re-wrote as: > > (define (valid-queen-moves board idx is-opposite-color?) > (append-map (λ (f) (apply f (list board idx is-opposite-color?))) > (list valid-bishop-moves valid-rook-moves))) > > I thought that was still ugly, so I re-wrote as: > > (define (valid-queen-moves . args) > (append-map (λ (f) (apply f args)) > (list valid-bishop-moves valid-rook-moves))) > > And it was at this point that I finally though, "This has to be a solved > problem already", but my initial searching turned up empty, so I wrote this: > > (define (unionify . functions) > (λ args (append-map (λ (f) (apply f args)) functions))) > > (define valid-queen-moves (unionify valid-bishop-moves valid-rook-moves)) > > unionify is a *terrible* name, but my question is whether this higher order > function already exists in the standard Racket library? I came close to > writing flat-map before I found append-map, so I don't want to reinvent > another wheel needlessly. > > Brian
Probably useless for your use case due to performance penalty, but in other cases `conjoin` might do the work: https://docs.racket-lang.org/reference/procedures.html?q=conjoin#%28def._%28%28lib._racket%2Ffunction..rkt%29._conjoin%29%29 -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
