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-rw-r--r--alist.scm55
1 files changed, 53 insertions, 2 deletions
diff --git a/alist.scm b/alist.scm
index 5917c7c..f1bdd70 100644
--- a/alist.scm
+++ b/alist.scm
@@ -1,5 +1,5 @@
;;;"alist.scm", alist functions for Scheme.
-;;;Copyright (c) 1992, 1993 Aubrey Jaffer
+;;;Copyright (c) 1992, 1993, 2003 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
@@ -8,7 +8,7 @@
;1. Any copy made of this software must include this copyright notice
;in full.
;
-;2. I have made no warrantee or representation that the operation of
+;2. I have made no warranty or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
@@ -17,6 +17,23 @@
;promotional, or sales literature without prior written consent in
;each case.
+;;@code{(require 'alist)}
+;;@ftindex alist
+;;
+;;Alist functions provide utilities for treating a list of key-value pairs
+;;as an associative database. These functions take an equality predicate,
+;;@var{pred}, as an argument. This predicate should be repeatable,
+;;symmetric, and transitive.
+;;
+;;Alist functions can be used with a secondary index method such as hash
+;;tables for improved performance.
+
+;;@body
+;;Returns an @dfn{association function} (like @code{assq}, @code{assv}, or
+;;@code{assoc}) corresponding to @var{pred}. The returned function
+;;returns a key-value pair whose key is @code{pred}-equal to its first
+;;argument or @code{#f} if no key in the alist is @var{pred}-equal to the
+;;first argument.
(define (predicate->asso pred)
(cond ((eq? eq? pred) assq)
((eq? = pred) assv)
@@ -30,12 +47,28 @@
((pred key (caar al)) (car al))
(else (l (cdr al)))))))))
+;;@body
+;;Returns a procedure of 2 arguments, @var{alist} and @var{key}, which
+;;returns the value associated with @var{key} in @var{alist} or @code{#f} if
+;;@var{key} does not appear in @var{alist}.
(define (alist-inquirer pred)
(let ((assofun (predicate->asso pred)))
(lambda (alist key)
(let ((pair (assofun key alist)))
(and pair (cdr pair))))))
+;;@body
+;;Returns a procedure of 3 arguments, @var{alist}, @var{key}, and
+;;@var{value}, which returns an alist with @var{key} and @var{value}
+;;associated. Any previous value associated with @var{key} will be
+;;lost. This returned procedure may or may not have side effects on its
+;;@var{alist} argument. An example of correct usage is:
+;;
+;;@lisp
+;;(define put (alist-associator string-ci=?))
+;;(define alist '())
+;;(set! alist (put alist "Foo" 9))
+;;@end lisp
(define (alist-associator pred)
(let ((assofun (predicate->asso pred)))
(lambda (alist key val)
@@ -44,6 +77,16 @@
alist)
(else (cons (cons key val) alist)))))))
+;;@body
+;;Returns a procedure of 2 arguments, @var{alist} and @var{key}, which
+;;returns an alist with an association whose @var{key} is key removed.
+;;This returned procedure may or may not have side effects on its
+;;@var{alist} argument. An example of correct usage is:
+;;
+;;@lisp
+;;(define rem (alist-remover string-ci=?))
+;;(set! alist (rem alist "foo"))
+;;@end lisp
(define (alist-remover pred)
(lambda (alist key)
(cond ((null? alist) alist)
@@ -58,9 +101,17 @@
(set-cdr! al (cddr al)) alist)
(else (l (cdr al)))))))))
+;;@body
+;;Returns a new association list formed by mapping @var{proc} over the
+;;keys and values of @var{alist}. @var{proc} must be a function of 2
+;;arguments which returns the new value part.
(define (alist-map proc alist)
(map (lambda (pair) (cons (car pair) (proc (car pair) (cdr pair))))
alist))
+;;@body
+;;Applies @var{proc} to each pair of keys and values of @var{alist}.
+;;@var{proc} must be a function of 2 arguments. The returned value is
+;;unspecified.
(define (alist-for-each proc alist)
(for-each (lambda (pair) (proc (car pair) (cdr pair))) alist))