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Guile programming language

Created 2022-07-07 Updated 2024-01-14

Anaphoric if

(define-syntax aif-version-1
  (lambda (x)
    (syntax-case x ()
      ((_ test then else)
       (with-syntax ((it (datum->syntax x 'it)))
         #'(let ((it test))
             (if it then else)))))))

(define-macro (aif-version-2 test then else)
              `(let ((it ,test))
                 (if it ,then ,else)))

(aif-version-2 2 (+ 1 it) 'bomb) ; => 3

Responses to the above code:

ctrl-c: Common Lisp Anaphoric IF

idiomdrottning: A problem with Guile’s defmacro

help

,in (cerbo stats) ,binding ; to see what's available
(help mid) ; get the document for a function MID

modules

Single: (use-modules (srfi srfi-19))

or multiple: (use-modules (srfi srfi-18) (srfi srfi-19))

srfi-19 Time/Date Library

ports

Read the output from a command:

(use-modules (ice-9 popen))

(define (read-command-v1 cmd)
  (define port (open-input-pipe cmd))
  (define str    (reverse-list->string     
                   (let loop ((char (read-char port))
                              (result '()))
                     (if (eof-object? char)
                       result           
                       (loop (read-char port) (cons char result))))))    
  (close-pipe port)    
  str)

(define (read-command-v2 cmd)
  (with-input-from-port (open-input-pipe cmd) read-string))

(display (read-command-v2 "ls -hal"))

procedures

cut: srfi-26

srfi

srfi-8 : receive: binding to multiple values

(receive (a b) (values 1 2) (displayln a) (displayln b)) ; 1 2

link

srfi-42 : Eager comprehensions

(list-ec (: i 5) (* i i)) => (0 1 4 9 16)
do-ec append-ec string-ec string-append-ec vector-ec ...

link

Exits

pipes: for reading or writing to system commands