Re: Adding wc to Bournish

[Efraim Flashner]

On Tue, Jun 14, 2016 at 01:20:29PM +0300, Efraim Flashner wrote:
> On Tue, Jun 14, 2016 at 11:57:26AM +0200, Ricardo Wurmus wrote:
> > 
> > Efraim Flashner <address@hidden> 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
> 

It turns out I forgot that calling only-files from wc-commands would
make it evaluate too soon, so I stuck it inside the different
implementations. Factoring out the check if a file exists or not could
also apply to the ls-command-implementation too later.


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Efraim Flashner   <address@hidden>   אפרים פלשנר
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0001-bournish-Add-wc-command.patch
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