Re: Adding wc to Bournish

[Efraim Flashner <efraim@flashner.co.il>]

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On Tue, Jun 14, 2016 at 11:57:26AM +0200, Ricardo Wurmus wrote:
> 
> Efraim Flashner <efraim@flashner.co.il> writes:
> 
> > +(define wc-command-implementation
> > +  (lambda files
> > +    (let ((files (filter (lambda (file)
> > +                           (catch 'system-error
> > +                             (lambda ()
> > +                               (stat file))
> > +                             (lambda args
> > +                               (let ((errno (system-error-errno args)))
> > +                                 (format (current-error-port) "~a: ~a~%"
> > +                                         file (strerror errno))
> > +                                 #f))))
> > +                         files)))
> > +      (for-each
> > +        (lambda (file)
> > +          (let-values (((lines chars)
> > +                        (call-with-input-file file lines+chars)))
> > +                      (format #t "~a ~a ~a~%" lines chars file)))
> > +        files))))
> > +
> > +(define wc-l-command-implementation
> > +  (lambda files
> > +    (let ((files (filter (lambda (file)
> > +                           (catch 'system-error
> > +                             (lambda ()
> > +                               (stat file))
> > +                             (lambda args
> > +                               (let ((errno (system-error-errno args)))
> > +                                 (format (current-error-port) "~a: ~a~%"
> > +                                         file (strerror errno))
> > +                                 #f))))
> > +                         files)))
> > +      (for-each
> > +        (lambda (file)
> > +          (let-values (((lines chars)
> > +                        (call-with-input-file file lines+chars)))
> > +                      (format #t "~a ~a~%" lines file)))
> > +        files))))
> > +
> > +(define wc-c-command-implementation
> > +  (lambda files
> > +    (let ((files (filter (lambda (file)
> > +                           (catch 'system-error
> > +                             (lambda ()
> > +                               (stat file))
> > +                             (lambda args
> > +                               (let ((errno (system-error-errno args)))
> > +                               (format (current-error-port) "~a: ~a~%"
> > +                                       file (strerror errno))
> > +                               #f))))
> > +                         files)))
> > +      (for-each
> > +        (lambda (file)
> > +          (let-values (((lines chars)
> > +                        (call-with-input-file file lines+chars)))
> > +                      (format #t "~a ~a~%" chars file)))
> > +        files))))
> 
> It looks to me that the filter function is the same in all of these
> procedures.  Even the actual implementation, i.e. the for-each over the
> resulting files is almost exactly the same.
> 
> This could be simplified.  If only the format expression differs then
> you could abstract this difference away.  You could still have three
> different procedures, but they can be the result of evaluating a
> higher-order function.
> 
> It also seems to me that you could use syntactic sugar to simplify
> “(define something (lambda ...))” to “(define (something ...))”.
> 
> ~~ Ricardo

It's already calling `((@@ (guix build bournish)
wc-l-command-implementation) ,@(delete "-l" args)), I could try changing
the ,@(delete part to ,@((@@ (guix build bournish) only-files) ,@(delete
"-l" args)) and then the various implementation functions will be just
printing the results

-- 
Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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