Thank you all, you have given me much to think on here. I had versions that used a generic function as suggested, but I wasn't sure if the cognitive overhead in understanding the generic strategy outweighed the benefits to concision. I think it probably does in some cases, probably related to how difficult it is to develop a good name for the generic function. However, in this case, I'm on board. Thank you for your time.
-Patrick On 8 May 2012 09:23, Matthias Felleisen <matth...@ccs.neu.edu> wrote: > > > On May 7, 2012, at 5:41 PM, Patrick Mahoney wrote: > > > #| > > Hello all, in a quest for greater concision, I'm looking for a way to > abstract over the following code containing mostly definitions. Is there an > accepted practice for abstraction over definition introduction?|# > > > > (define top-right-x > > (lambda (a-grid-plane a-cell) > > > > ;;The next three definitions are what I am looking to abstract over, as > they show up in many similarly defined functions.|# > > (match-define (cell row-pos col-pos) a-cell) > > > > (define cell-size (grid-plane->cell-size a-grid-plane)) > > > > (match-define (size cell-w cell-h) cell-size) > > > > (+ cell-w > > (* col-pos cell-w)))) > > > > (define top-right-y > > (lambda (a-grid-plane a-cell) > > > > (match-define (cell row-pos col-pos) a-cell) > > > > (define cell-size (grid-plane->cell-size a-grid-plane)) > > > > (match-define (size cell-w cell-h) cell-size) > > > > (* row-pos cell-w))) > > > > #|How should I approach this? are my options parameters, leaving as is, > a with- macro? > > > 1. Define a higher-order function that computes these things: > > (define (vertical-horizontal body) > (lambda (a-grid-plane a-cell) > ... defines ... > (body cell-w col-pos row-pos))) ;; you may need additional parameters > > (define top-right-x (vertical-horizontal (lambda (cell-w col-pos row-pos) > (+ cell-w (* col-pos cell-w))) > ... > > That's the best solution. > > 2. Define a macro for the entire function, not just the three auxiliaries. > See 1, but perhaps less notation. > > 3. If the above is only a hint at how complex your definitions may get, > read up on units. Units are modules abstracted over context, i.e., bundles > over definitions abstracted over other definitions, possibly mutually > recursive. > > -- Matthias > >
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