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Diffstat (limited to 'doc/ref/scheme-scripts.texi')
-rw-r--r-- | doc/ref/scheme-scripts.texi | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/doc/ref/scheme-scripts.texi b/doc/ref/scheme-scripts.texi index 296bea772..d845148ba 100644 --- a/doc/ref/scheme-scripts.texi +++ b/doc/ref/scheme-scripts.texi @@ -293,6 +293,11 @@ and exit. Load the file @file{/u/jimb/ex4}, and then call the function @code{main}, passing it the list @code{("/u/jimb/ex4" "foo")}. +@item guile -e '(ex4)' -s /u/jimb/ex4.scm foo +Load the file @file{/u/jimb/ex4.scm}, and then call the function +@code{main} from the module '(ex4)', passing it the list +@code{("/u/jimb/ex4" "foo")}. + @item guile -l first -ds -l last -s script Load the files @file{first}, @file{script}, and @file{last}, in that order. The @code{-ds} switch says when to process the @code{-s} @@ -369,6 +374,7 @@ Suppose that we now want to write a script which computes the @code{(choose @var{n} @var{m})} is the number of distinct subsets containing @var{n} objects each. It's easy to write @code{choose} given @code{fact}, so we might write the script this way: + @example #!/usr/local/bin/guile \ -l fact -e main -s @@ -402,6 +408,68 @@ $ ./choose 50 100 100891344545564193334812497256 @end example +To call a specific procedure from a given module, we can use the special +form @code{(@@ (@var{module}) @var{procedure})}: + +@example +#!/usr/local/bin/guile \ +-l fact -e (@@ (fac) main) -s +!# +(define-module (fac) + #:export (main)) + +(define (choose n m) + (/ (fact m) (* (fact (- m n)) (fact n)))) + +(define (main args) + (let ((n (string->number (cadr args))) + (m (string->number (caddr args)))) + (display (choose n m)) + (newline))) +@end example + +We can use @code{@@@@} to invoke non-exported procedures. For exported +procedures, we can simplify this call with the shorthand +@code{(@var{module})}: + +@example +#!/usr/local/bin/guile \ +-l fact -e (fac) -s +!# +(define-module (fac) + #:export (main)) + +(define (choose n m) + (/ (fact m) (* (fact (- m n)) (fact n)))) + +(define (main args) + (let ((n (string->number (cadr args))) + (m (string->number (caddr args)))) + (display (choose n m)) + (newline))) +@end example + +For maximum portability, we can instead use the shell to execute +@command{guile} with specified command line arguments. Here we need to +take care to quote the command arguments correctly: + +@example +#!/usr/bin/env sh +exec guile -l fact -e '(@@ (fac) main)' -s "$0" "$@" +!# +(define-module (fac) + #:export (main)) + +(define (choose n m) + (/ (fact m) (* (fact (- m n)) (fact n)))) + +(define (main args) + (let ((n (string->number (cadr args))) + (m (string->number (caddr args)))) + (display (choose n m)) + (newline))) +@end example + Finally, seasoned scripters are probably missing a mention of subprocesses. In Bash, for example, most shell scripts run other programs like @code{sed} or the like to do the actual work. |