On Tuesday, November 15, 2016 at 11:53:37 AM UTC-5, johnbclements wrote:
> > On Nov 15, 2016, at 8:30 AM, Brian Adkins <lojicdot...@gmail.com> 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 personally find this first one the most readable.
>
> If you don’t like it, you could always bundle the arguments together into
> something called state, so that it reads:
>
> (define (valid-queen-moves state)
> (append (valid-bishop-moves state)
> (valid-rook-moves state)))
That's a good point, and takes care of one of my original objects, but I'm not
sure it's as clear for indicating that baz simply combines the results of foo &
bar, for example:
(define valid-queen-moves
(juxt valid-bishop-moves
valid-rook-moves))
"juxt" is probably still not the best name, but better than my "unionify" which
isn't even technically a union with respect to sets :)
>
> …
>
> but honestly, I think that the way you wrote it at first is probably the
> best. IMHO.
>
> John Clements
>
> >
> > 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
> >
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