Re: Adding wc to Bournish

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

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On Wed, Jun 08, 2016 at 05:43:09PM +0200, Ludovic Courtès wrote:
> Efraim Flashner <efraim@flashner.co.il> skribis:
> 
> > On Sun, Jun 05, 2016 at 10:37:12PM +0200, Ludovic Courtès wrote:
> 
> [...]
> 
> >> I’ll commit a couple of fixes for bugs I just found and that prevent us
> >> from doing:
> >> 
> >>   (compile "ls" #:from %bournish-language #:to 'scheme).
> 
> (This should be be ‘read-and-compile’, not ‘compile’.)
> 
> Done in f82c58539e1f7b9b864e68ea2ab0c6a17c15fbb5.  Take a look at
> tests/bournish.scm for examples of what is expected.
> 

ok

> > From ebce5076177314bfd17a53019b3f6b6888762b01 Mon Sep 17 00:00:00 2001
> > From: Efraim Flashner <efraim@flashner.co.il>
> > Date: Sun, 22 May 2016 14:56:06 +0300
> > Subject: [PATCH] bournish: Add `wc' command.
> >
> > * guix/build/bournish.scm (file-size, wc-c-command, wc-l-command,
> > lines+chars, wc-command, wc-command-implementation): New variables.
> > (%commands): Add wc command.
> 
> [...]
> 
> > +(define* (wc-command-implementation filelist #:optional args)
> 
> ‘files’, not ‘filelist’.
> 

ok

> > +  (let ((files (filter (lambda (file)
> > +                         (catch 'system-error
> > +                           (lambda ()
> > +                             (lstat file))
> > +                           (lambda args
> > +                              (let ((errno (system-error-errno args)))
> > +                               (format (current-error-port) "~a: ~a~%"
> > +                                       file (strerror errno))
> > +                               #f))))
> 
> ‘stat’ rather than ‘fstat’.
> 

ok

> > +    (for-each
> > +      (lambda (file)
> > +        (let-values (((lines chars)
> > +                      (call-with-input-file file lines+chars)))
> > +                    (match args
> > +                      (#\l
> > +                       (format #t "~a ~a~%" lines file))
> > +                      (#\c
> > +                       (format #t "~a ~a~%" chars file))
> > +                      (_
> > +                       (format #t "~a ~a ~a~%" lines chars file)))))
> > +      files)))
> 
> OK.
> 

In the end I went with 3 separate functions for the three commands
(`wc', `wc -l', `wc -c') like you mentioned later.

> > +(define (wc-command args . rest)
> > +  (let* ((flags (cond ((string=? args "-l") #\l)
> > +                      ((string=? args "-c") #\c)
> > +                      (else #\nul))))    ; no flags, "args" is a file
> 
> I’d rather make it:
> 
>   (define (wc-commands . args)
>     (cond ((member "-l" args) …)
>           ((member "-c" args) …)
>           (else …)))
> 
> Instead of the #\nul thing, I think it’d be best to have separate
> procedures for -l, -c, and the other case.

This also looks nicer, and I was able to strip the `-l' or `-c' before
passing the ,args to the implementation function.

> 
> > +    ((@@ (guix build bournish) wc-command-implementation)
> > +     (if (char=? flags #\nul) (cons args rest) rest) flags)))
> 
> This is still not emitting code.  :-)  IOW, there should be a quasiquote
> here.
> 
> You can see that by running:
> 
>   (use-modules (system base compile) (guix build bournish))
>   (read-and-compile (open-input-string "wc -l foo")
>                     #:from %bournish-language #:to 'scheme)
> 
> This should return something like:
> 
>   `((@ (guix build bournish) wc-l-command-implementation) '("foo"))
> 

got this one fixed, which in turn broke the implementation code ;) In
the end I went with not a list, so it came out like this:

scheme@(guile-user)> (read-and-compile (open-input-string "wc -l foo bar baz") #:from %bournish-language #:to 'scheme)
$1 = ((@@ (guix build bournish) wc-l-command-implementation) "foo" "bar" "baz")

> Makes sense?  We’re almost done.
> 
> Please take a look at
> <https://www.gnu.org/software/guix/manual/html_node/Coding-Style.html>
> to make the last review super fast.  ;-)
> 
> Thank you!
> 
> Ludo’.

I've attached what hopefully is the last patch for wc :) I took (and put
somewhere safe) the other code I wrote that does wc-c by calling (stat
file) and the one for wc-l that opens the file as a port and reads for
#\newlines.

-- 
Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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From 60a473e123a5da4e3592c67aae8002bf11cca633 Mon Sep 17 00:00:00 2001
From: Efraim Flashner <efraim@flashner.co.il>
Date: Sun, 22 May 2016 14:56:06 +0300
Subject: [PATCH] bournish: Add `wc' command.

* guix/build/bournish.scm (lines+chars, wc-commands,
wc-command-implementation, wc-l-command-implementation,
wc-c-command-implementation): New variables.
(%commands): Add wc command.
---
 guix/build/bournish.scm | 79 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 78 insertions(+), 1 deletion(-)

diff --git a/guix/build/bournish.scm b/guix/build/bournish.scm
index 1f17e0a..a4c5b83 100644
--- a/guix/build/bournish.scm
+++ b/guix/build/bournish.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016 Efraim Flashner <efraim@flashner.co.il>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -25,6 +26,7 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 ftw)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-26)
   #:export (%bournish-language))
 
@@ -103,6 +105,80 @@ characters."
        ((@ (guix build utils) dump-port) port (current-output-port))
        *unspecified*)))
 
+(define (lines+chars port)
+  ;; Return the number of lines and number of chars read from PORT.
+  ;; TODO: Also return the number of words.
+  (let loop ((lines 0) (chars 0))
+    (match (read-char port) ; get the next char ready
+      ((? eof-object?)              ;done!
+       (values lines chars))
+      (#\newline                    ;recurse
+       (loop (1+ lines) (1+ chars)))
+      (_                            ;recurse
+       (loop lines (1+ chars))))))
+
+(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))))
+
+(define (wc-commands . args)
+  (cond ((member "-l" args) `((@@ (guix build bournish) wc-l-command-implementation) ,@(delete "-l" args)))
+        ((member "-c" args) `((@@ (guix build bournish) wc-c-command-implementation) ,@(delete "-c" args)))
+        (else `((@@ (guix build bournish) wc-command-implementation) ,@args))))
+
 (define (help-command . _)
   (display "\
 Hello, this is Bournish, a minimal Bourne-like shell in Guile!
@@ -129,7 +205,8 @@ commands such as 'ls' and 'cd'; it lacks globbing, pipes---everything.\n"))
     ("help"   ,help-command)
     ("ls"     ,ls-command)
     ("which"  ,which-command)
-    ("cat"    ,cat-command)))
+    ("cat"    ,cat-command)
+    ("wc"     ,wc-commands)))
 
 (define (read-bournish port env)
   "Read a Bournish expression from PORT, and return the corresponding Scheme
-- 
2.8.4


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