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Article contents:== Outdated egg! This is an egg for CHICKEN 3, the unsupported old release. You're almost certainly looking for [[/eggref/4/procedure-decoration|the CHICKEN 4 version of this egg]], if it exists. If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-4.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN. [[tags: egg]] [[toc:]] == Introduction {{Chicken Scheme}} procedures have attributes, aspects of the procedure object that can be operated upon. Such an attribute is known as a "procedure decoration". This extension provides a facility to perform procedure decoration operations. == Usage (require-extension procedure-decoration) == Documentation An interface for procedure decoration. Similar to the lolevel unit {{extend-procedure}} interface but allowing many decorations, not just one. == Lambda Decoration Interface A lower level interface for procedure decoration. A {{PREDICATE}} is a procedure of one argument, a procedure decoration. The predicate must return a {{boolean}} indicating whether the argument is a decoration of the proper kind. A {{DECORATOR}} is a procedure of one argument, the current procedure decoration. The decorator must return an object to replace the current decoration. === decorate-lambda [procedure] (decorate-lambda PROCEDURE PREDICATE DECORATOR) Decorate the {{PROCEDURE}} per the {{PREDICATE}} with the result of the {{DECORATOR}}. Returns the decorated procedure. === decorated-lambda? [procedure] (decorated-lambda? PROCEDURE PREDICATE) Is the {{PROCEDURE}} decorated per the {{PREDICATE}}? === lambda-decoration [procedure] (lambda-decoration PROCEDURE PREDICATE) === set-lambda-decoration! [procedure] (set-lambda-decoration! PROCEDURE PREDICATE DECORATOR) Change the decoration of the {{PROCEDURE}} per the {{PREDICATE}} with the result of the {{DECORATOR}}. The {{PROCEDURE}} must be already decorated per the {{PREDICATE}}. Returns the decorated procedure. == Procedure Decorator Interface A more sophisticated interface for procedure decoration. === make-procedure-decorator [procedure] (make-procedure-decorator PREDICATE DECORATOR RETRIEVER [#:INITIALIZER] [#:INITIAL-VALUE] [#:BECOME?]) Returns a new {{procedure-decorator}}. A {{PREDICATE}} is a procedure of one argument, a procedure decoration. The predicate must return a {{boolean}} indicating whether the argument is a decoration of the proper kind. A {{DECORATOR}} is a procedure at least one argument, a procedure decoration. The decorator must return an object to replace the existing decoration. The {{RETRIEVER}} is a procedure of varying arity, returning the procedure decoration object. The first argument is the procedure decoration. Any following arguments are from the {{procedure-decoration}} call that will invoke the {{RETRIEVER}}. The {{INITIAL-VALUE}} is used as the procedure decoration for the first invocation of {{decorate-procedure}}. If not supplied an {{INITIALIZER}} must be available. The {{INITIALIZER}} is a procedure of varying arity, returning the procedure decoration initial object. The arguments are from the {{decorate-procedure}} call that invokes the {{INITIALIZER}}. The {{INITIALIZER}} is invoked only once per procedure to decorate. The default {{INITIALIZER}} is built from the {{DECORATOR}}. When an {{INITIAL-VALUE}} is not supplied the default {{DECORATOR}} will be called with a first argument of {{(void)}}, and any other arguments from the {{decorate-procedure}} call. Otherwise the default {{DECORATOR}} will be called with a first argument of {{(void)}} and the {{INITIAL-VALUE}} as the second argument; any arguments from {{decorate-procedure}} call are ignored. The {{BECOME?}} flag determines whether the procedure object of a decorated procedure will be rewritten. The default is {{#f}}. === procedure-decorator? [procedure] (procedure-decorator? OBJECT) Is the {{OBJECT}} a {{procedure-decorator}}? === procedure-decorator-become? [procedure] (procedure-decorator-become? PROCEDURE-DECORATOR) Is the {{PROCEDURE-DECORATOR}} a {{BECOME?}} decorator? === decorate-procedure [procedure] (decorate-procedure PROCEDURE PROCEDURE-DECORATOR [ARGUMENTS ...]) Decorate the {{PROCEDURE}} with the {{PROCEDURE-DECORATOR}}. The {{PROCEDURE-DECORATOR}} {{INITIALIZER}} is called on the first invocation for {{PROCEDURE}} and the {{DECORATOR}} on all subsequent invocations. The optional {{ARGUMENTS}} are passed to the invoked {{PROCEDURE-DECORATOR}} constructor, as above. On the first invocation a {{GC}} will be performed. Returns the decorated procedure. === decorated-procedure? [procedure] (decorated-procedure? PROCEDURE PROCEDURE-DECORATOR) Is the {{PROCEDURE}} a decorated by {{PROCEDURE-DECORATOR}}? === procedure-decoration [procedure] (procedure-decoration PROCEDURE PROCEDURE-DECORATOR [ARGUMENTS ...]) Returns the procedure decoration of {{PROCEDURE-DECORATOR}} for the {{PROCEDURE}}. The optional {{ARGUMENTS}} are passed to the {{PROCEDURE-DECORATOR}} {{RETRIEVER}}. === procedure-decorator-getter-and-setter [procedure] (procedure-decorator-getter-and-setter PROCEDURE-DECORATOR) Returns a single argument getter, and creates a two argument setter, for the {{PROCEDURE-DECORATOR}}. The getter takes a {{PROCEDURE}} argument. The setter takes {{PROCEDURE}} and {{OBJECT}} arguments. == Procedure Extender Not to be confused with the lolevel unit {{extend-procedure}} interface. === make-procedure-extender [procedure] (make-procedure-extender TAG) Returns a simple {{PROCEDURE-DECORATOR}} that recognizes its' decorations by the {{TAG}} and accepts any object as a decoration. The {{TAG}} may be any object but is usually a {{symbol}}. === define-procedure-extender [syntax] (define-procedure-extender TAG [GETTER-NAME] [PREDICATE-NAME]) Creates a functional interface for a {{PROCEDURE-EXTENDER}} that uses the {{TAG} symbol. Defines the {{PROCEDURE-DECORATOR}} as {{TAG-decorator}}. Defines a procedure named {{GETTER-NAME}} that takes one argument, a decorated procedure, and returns the procedure decoration. Creates a corresponding setter. The default {{GETTER-NAME}} is {{TAG-decoration}}. Defines a procedure named {{PREDICATE-NAME}} that takes one argument, a procedure, and returns whether the procedure is decorated. The default {{PREDICATE-NAME}} is {{TAG-decorated?}}. == Miscellaneous === lambda->list [procedure] (lambda->list PROCEDURE [START] [END]) Returns the procedure object items of {{PROCEDURE}} from {{START}} to {{END}} as a list. The {{START}} default is 1. The {{END}} default is the number of procedure object items. Use of this procedure is potentially dangerous if any of the objects in the list are mutated. Do not mutate the objects! Even better, do not use this procedure! == Examples Using a new define syntax (works for compiled or interpreted procedures). <enscript language=scheme> (use procedure-decoration) (use (srfi 89)) ;; Procedure documentation string API (define-procedure-extender docstring procedure-documentation documented-procedure?) ;; Procedure documentation 'define' wrappers ; Common code helper (define-macro ($define/doc ?defknd ?head ?docstr ?body) (let ([nam (let loop ([hd ?head]) (if (pair? hd) (loop (car hd)) hd))]) `(begin (,?defknd ,?head ,@?body) (set! (procedure-documentation ,nam) ,?docstr) (begin) ) ) ) ; Chicken 'define' (define-macro (define/doc ?head ?docstr . ?body) `($define/doc define ,?head ,?docstr ,?body) ) ; Chicken SRFI-89 'define*' (define-macro (define*/doc ?head ?docstr . ?body) `($define/doc define* ,?head ,?docstr ,?body) ) ;; Try it out (define/doc (foo . args) "procedure is foo" #t ) (procedure-documentation foo) ;=> "procedure is foo" (define*/doc (h2 (key: k #f) a . r) "h2 is srfi-89 proc" (list a k r)) (procedure-documentation h2) ;=> "h2 is srfi-89 proc" </enscript> Using original define syntax, for compile-time only. Must be used as a compiler extension. <enscript language=scheme> (use procedure-decoration) (let () (define-procedure-extender docstring lambda-documentation) (set! ##compiler#process-lambda-documentation (lambda (id doc proc) (set! (lambda-documentation proc) doc) proc)) ) </enscript> == Notes The {{decorate-lambda}} interface decorated procedure is not the original procedure. Decorating procedure {{foo}} will not change the procedure object of {{foo}}, but return a new one. The {{procedure-decorator}} interface can rewrite the procedure object. Decorating procedure {{foo}} with a {{BECOME?}} {{procedure-decorator}} changes the procedure object of {{foo}}. == Author Kon Lovett == License Copyright (c) 2008 Kon Lovett. All rights reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the Software), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED ASIS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. == Requirements misc-extn == Version history ; 1.0 : Description of your changes:

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