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| | ;; _unknown.scm -- An example for an `unknown' service.
;; Copyright (C) 2003 Wolfgang Jährling <wolfgang@pro-linux.de>
;;
;; This file is part of the GNU Shepherd.
;;
;; The GNU Shepherd is free software; you can redistribute it and/or modify it
;; under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3 of the License, or (at
;; your option) any later version.
;;
;; The GNU Shepherd is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with the GNU Shepherd. If not, see <http://www.gnu.org/licenses/>.
;; Return true if STR1 lacks a character that exists in STR2, but
;; otherwise both are identical.
(define (lacks-char-from? str1 str2)
(and (= (string-length str1)
(+ (string-length str2) 1))
(letrec ((next
(lambda (pos)
(and (not (= pos (string-length str1)))
(or (string=? str2
(string-append
(substring str1 0 pos)
(substring str1
(+ pos 1)
(string-length str1))))
(next (+ pos 1)))))))
(next 0))))
;; Return true if either of STR1 and STR2 lacks a character found in
;; the other one, but otherwise both are identical (e.g. as is the
;; case for "blah" and "bla").
(define (differs-by-missing-char? str1 str2)
(or (lacks-char-from? str1 str2)
(lacks-char-from? str2 str1)))
;; Return true if the only difference between STR1 and STR2 is that a
;; successive pair of characters is switched in one of them.
(define (differs-by-switched-chars? str1 str2)
(and (= (string-length str1)
(string-length str2))
(> (string-length str1) 1)
(letrec ((next
(lambda (pos)
(and (not (= pos (string-length str1)))
(or (string=? str2
(string-append
(substring str1 0 (- pos 1))
(string (string-ref str1 pos)
(string-ref str1 (- pos 1)))
(substring str1
(+ pos 1)
(string-length str1))))
(next (+ pos 1)))))))
(next 1))))
;; Return true if they differ by exactly one character (e.g. as is the
;; case for "blah" and "bleh"), if it isn't the only one.
(define (differs-by-one-char? str1 str2)
(and (= (string-length str1)
(string-length str2))
(> (string-length str1) 1)
(letrec ((next
(lambda (pos found-difference)
(if (= pos (string-length str1))
found-difference
(if (char=? (string-ref str1 pos)
(string-ref str2 pos))
(next (+ pos 1) found-difference)
(and (not found-difference)
(next (+ pos 1) #t)))))))
(next 0 #f))))
;; Return true if STR1 and STR2 are identical, except for case
;; (e.g. this gives true for "foobar" and "FooBAR").
(define (differs-only-in-case? str1 str2)
(and (not (string=? str1 str2))
(string-ci=? str1 str2)))
;; Return true if STR1 and STR2 are `similar' strings, meaning that
;; they only differ in a minor way.
(define (similar? str1 str2)
(any (lambda (pred?)
(pred? str1 str2))
(list differs-by-missing-char?
differs-by-switched-chars?
differs-by-one-char?
differs-only-in-case?)))
\f
;; TODO
;; - We could look for non-running services first on `start' etc.
;; - We also should do `unknown-action' (if service is known)
;; - If doing this, we should enable the service to handle it
;; - Make this the `default unknown service'
;; - Messages if nothing found.
;; Suggest a service that satisfies PRED?, if given, and has a name
;; similar to SERVICE-SYMBOL.
(define look-for-service
(case-lambda
((service-symbol) (look-for-service service-symbol (lambda (x) #t)))
((service-symbol pred?)
(call/ec
(lambda (return)
(for-each-service
(lambda (s)
(and (pred? s)
(similar? (symbol->string service-symbol)
(symbol->string (canonical-name s)))
(begin
(format #t "Did you mean ~a maybe?" (canonical-name s))
(newline)
(return #t)))))
#f)))))
;; The classical compose.
(define (compose f g)
(lambda (x)
(f (g x)))
(define unknown-service
(make <service>
#:provides '(unknown)
#:actions (make-actions
(start
"Called if user wants to start an unknown service."
(lambda (running service-sym . args)
(or (look-for-service service-sym (compose not running?))
(look-for-service service-sym))
running))
(stop
"Called if user wants to stop an unknown service."
(lambda (running service-sym . args)
(or (look-for-service service-sym running?)
(look-for-service service-sym))
running))
(action
"Called if user frobs an unknown service."
(lambda (running service-sym the-action . args)
(or (look-for-service service-sym running?)
(look-for-service service-sym))
running)))))
(register-services unknown-service)
(start unknown-service)
|