From patchwork Thu Dec 28 00:29:43 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Skyler Ferris X-Patchwork-Id: 58121 Return-Path: X-Original-To: patchwork@mira.cbaines.net Delivered-To: patchwork@mira.cbaines.net Received: by mira.cbaines.net (Postfix, from userid 113) id D2D2B27BBEA; Thu, 28 Dec 2023 00:31:30 +0000 (GMT) X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on mira.cbaines.net X-Spam-Level: X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,FREEMAIL_FROM,MAILING_LIST_MULTI,SPF_HELO_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mira.cbaines.net (Postfix) with ESMTPS id 99A8927BBE2 for ; Thu, 28 Dec 2023 00:31:28 +0000 (GMT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rIeIl-0003tn-Ag; Wed, 27 Dec 2023 19:31:07 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rIeIi-0003tR-LU for guix-patches@gnu.org; Wed, 27 Dec 2023 19:31:04 -0500 Received: from debbugs.gnu.org ([2001:470:142:5::43]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1rIeIh-0001xc-SH for guix-patches@gnu.org; Wed, 27 Dec 2023 19:31:04 -0500 Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1rIeIg-000679-DO for guix-patches@gnu.org; Wed, 27 Dec 2023 19:31:02 -0500 X-Loop: help-debbugs@gnu.org Subject: [bug#67786] doc: Add documentation for define-record-type* References: <9bf2efa9c7aab1661fcf5180d1e536fc6dc0e9b3.1702324538.git.skyvine@protonmail.com> In-Reply-To: <9bf2efa9c7aab1661fcf5180d1e536fc6dc0e9b3.1702324538.git.skyvine@protonmail.com> Resent-From: Skyler Ferris Original-Sender: "Debbugs-submit" Resent-CC: guix-patches@gnu.org Resent-Date: Thu, 28 Dec 2023 00:31:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 67786 X-GNU-PR-Package: guix-patches X-GNU-PR-Keywords: patch To: 67786@debbugs.gnu.org Received: via spool by 67786-submit@debbugs.gnu.org id=B67786.170372340615963 (code B ref 67786); Thu, 28 Dec 2023 00:31:02 +0000 Received: (at 67786) by debbugs.gnu.org; 28 Dec 2023 00:30:06 +0000 Received: from localhost ([127.0.0.1]:38097 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1rIeHk-00046l-9r for submit@debbugs.gnu.org; Wed, 27 Dec 2023 19:30:05 -0500 Received: from mail-40134.protonmail.ch ([185.70.40.134]:57475) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1rIeHf-00041i-PD for 67786@debbugs.gnu.org; Wed, 27 Dec 2023 19:30:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail3; t=1703723393; x=1703982593; bh=edeYyfdsS4v0Ic9L8nZdhj7i9ZGMg7t/ZNMhci1azgA=; h=Date:To:From:Subject:Message-ID:Feedback-ID:From:To:Cc:Date: Subject:Reply-To:Feedback-ID:Message-ID:BIMI-Selector; b=U3dp0Mw0ZhHT4ooRb5i0NTSajEM63uE8YzQBZ8olAD/acsh8lrr22bujh2aqPLine 3fhW7sh2rzNVNrkxy610GU8zHVqbZHblHRtQQSvVk+16QFUfDXg1/vq7eh7WH4oqrO TFP482xa/3ZsLfovXFxSByy6YW7TIbiQ7E5zTgfOe6ipPLp27iZwZgq8ZbytNs+kav HkmKVA1CaLAwp6xvPHrphw3Xuvkf7bEi1W9KbKF+2ek4gDa4GrG1DUr8JOoK2DtuPG Vd1RXAZii1Vflbhv1tnDJH9r5jxDk/yQoGbv8l7QFlNWS9AB6dLlo3lCRTMSgLmlTo YyZrLSIAN2+2A== Date: Thu, 28 Dec 2023 00:29:43 +0000 Message-ID: <10d46484-1f83-4b5f-9cc7-3d9d68998b33@protonmail.com> Feedback-ID: 40635331:user:proton MIME-Version: 1.0 X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: guix-patches@gnu.org List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-to: Skyler Ferris X-ACL-Warn: , Skyler Ferris via Guix-patches X-Patchwork-Original-From: Skyler Ferris via Guix-patches via From: Skyler Ferris Errors-To: guix-patches-bounces+patchwork=mira.cbaines.net@gnu.org Sender: guix-patches-bounces+patchwork=mira.cbaines.net@gnu.org X-getmail-retrieved-from-mailbox: Patches I wrote this documentation by using the docstring in guix/record.scm as a starting point and expanding on it/reformatting on it to be appropriate for inclusion in a manual. * doc/guix.texi: Add sections describing the typical usage and API for define-record-type* Change-Id: I19e7220553d10652c794e6e0172b2c9ee961f54f --- # This version of the patch updates the commit message to explain that I # wrote the documentation by using the docstring in guix/records.scm as # a starting point. This process seemed appropriate to me because it is # being incorporated into the same project for the same purpose. Most of # the commit is new content, but some of it is shared with the docstring # - for example the "thing" struct definition and the explanation of # thunked. I think that it is useful for the manual and the # docstrings to share content when appropriate to avoid accidentally # communicating contradictory ideas to different audiences, but the # relationship should still be acknowledged. If there is a more formal # manner in which I should indicate this please let me know and I will # be happy to update the commit. This version does not change anything # other than the commit message.  doc/contributing.texi |   1 -  doc/guix.texi         | 274 ++++++++++++++++++++++++++++++++++++++++++  2 files changed, 274 insertions(+), 1 deletion(-) +(define derived-rectangle +  (rectangle +    (inherit base) +    (width   6))) + +(rectangle-area base-rectangle) +@result{} 8 + +(rectangle-area derived-rectangle +@result{} 24 +@end lisp + +@item (delayed) +Fields marked as @code{delayed} are similar to @code{thunked} fields, except +that they are effectively wrapped in a @code{(delay @dots{})} form. Note that +delayed fields cannot use @code{this-identifier}. +@end table +@end table +@end defmac +  @node Invoking guix repl  @section Invoking @command{guix repl} diff --git a/doc/contributing.texi b/doc/contributing.texi index 7337f4bd58..d920b2589a 100644 --- a/doc/contributing.texi +++ b/doc/contributing.texi @@ -1313,7 +1313,6 @@ Data Types and Pattern Matching  notably the fact that it is hard to read, error-prone, and a hindrance  to proper type error reports. -@findex define-record-type*  @findex match-record  @cindex pattern matching  Guix code should define appropriate data types (for instance, using diff --git a/doc/guix.texi b/doc/guix.texi index e61a893af9..3cb15eeca3 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -12606,6 +12606,280 @@ G-Expressions  @code{(*approximate*)}, but this may change.  @end deffn +@node Records in Guix +@section Records in Guix +Guix uses @code{define-record-type*} to define structures with a lispy format. +Packages, operating systems, etc are all defined with +@code{define-record-type*} facilities. If one was using this facility to +define preferences for a text editor, it might look like this: + +@lisp +;; The only valid emulation modes are the symbol 'emacs, the symbol 'vim, or +;; the boolean #f. As a convenience to the user, if they pass in a string +;; first convert it to a symbol and accept it if it is valid. +(define (sanitize-emulation-mode value) +  (let ((symbolized-value (cond ((not value)     #f) +                                ((string? value) (string->symbol value)) +                                (#t              value)))) +    (unless (or (not symbolized-value) +                (eq? symbolized-value 'emacs) +                (eq? symbolized-value 'vim)) +      (throw 'bad-emulation-made +             (format #f "Unrecognized emulation mode: ~s" value))) +    symbolized-value)) + +(define-record-type* +  editor-preferences make-editor-preferences +  editor-preferences? this-editor-preferences +  (background-color editor-preferences-background-color +                    (default "000000")) +  (text-color       editor-preferences-text-color +                    (default "FFFFFF")) +  (emulation-mode   editor-preferences-emulation-mode +                    (default #f) +                    (sanitize sanitize-emulation-mode))) +@end lisp + +A user could then define their preferences like this: + +@lisp +(define my-preferences +  (editor-preferences +    (background-color "222222") +    (emulation-mode   'vim))) +@end lisp + +The value contained in @code{my-preferences} contains a custom +@code{background-color} and @code{emulation-mode}, but keeps the default +@code{text-color} (@code{"FFFFFF"}). If an invalid @code{emulation-mode} had +been specified, for example if the user passed in @code{"vi"} instead of +@code{"vim"}, @code{sanitize-emulation-mode} would immediately throw an error. + +The program can access values like this: + +@lisp +(editor-preferences-background-color my-preferences) +@result{} "222222" +(editor-preferences-text-color my-preferences) +@result{} "FFFFFF" +(editor-preferences-emulation-mode my-preferences) +@result{} 'vim +@end lisp + +There is no way to define setters (all instances are immutable). + +@node Record Inheritance +@subsection Record Inheritance +It is also possible to inherit from previously defined instances when creating +new ones. Continuing with the editor example, someone might want to base their +preferences on their friend's preferences but customize a value: + +@lisp +(define friends-preferences +  (editor-preferences +    (inherit my-preferences) +    (emulation-mode 'emacs))) +@end lisp + +This keeps the same @code{background-color} and @code{text-color} that are +contained in @code{my-preferences} but changes the @code{emulation-mode} to +be @code{'emacs} instead of @code{'vim}. + +Sometimes it does not make sense for a field to be inherited. Suppose that the +@code{} type is updated to contain a username so that a +friendly greeting can be displayed when the program starts up: + +@lisp +;; Usernames must be strings. It would be strange to pass a username as a +;; symbol, so throw an error in case the user meant to pass in a variable's +;; value instead of a literal symbol. +(define (sanitize-username value) +  (unless (string? value) +    (throw 'bad-username +           (format #f "Usernames must be strings! Got: ~s" value))) +  value) + +(define (sanitize-emulation-mode value) +  (let ((symbolized-value (cond ((not value)     #f) +                                ((string? value) (string->symbol value)) +                                (#t              value)))) +    (unless (or (not symbolized-value) +                (eq? symbolized-value 'emacs) +                (eq? symbolized-value 'vim)) +      (throw 'bad-emulation-made +             (format #f "Unrecognized emulation mode: ~s" value))) +    symbolized-value)) + +(define-record-type* +  editor-preferences make-editor-preferences +  editor-preferences? this-editor-preferences +  (username         editor-preferences-username +                    (innate) +                    (sanitize sanitize-username)) +  (background-color editor-preferences-background-color +                    (default "000000")) +  (text-color       editor-preferences-text-color +                    (default "FFFFFF")) +  (emulation-mode   editor-preferences-emulation-mode +                    (default #f) +                    (sanitize sanitize-emulation-mode))) +@end lisp + +There are a couple of differences in the new @code{username} field compared to +the fields we looked at earlier. It is marked as @code{innate}, which means +that it will not be inherited. For example, consider what would happen if we +tried to define new instances like this: + +@lisp +(define my-preferences +  (editor-preferences +    (username         "my-username") +    (background-color "222222") +    (emulation-mode   'vim))) + +(define friends-preferences +  (editor-preferences +    (inherit my-preferences) +    (emulation-mode 'emacs))) +@end lisp + +While the @code{friends-preferences} instance still inherits the values for +@code{background-color} and @code{text-color}, it will not inherit the value +for @code{username}. Furthermore, as the @code{username} field does not define +a default value the attempted creation of @code{friends-preferences} will +actually throw an error. Instead, we could do this: + +@lisp +(define my-preferences +  (editor-preferences +    (username         "my-username") +    (background-color "222222") +    (emulation-mode   'vim))) + +(define friends-preferences +  (editor-preferences +    (inherit        my-preferences) +    (username       "friends-username") +    (emulation-mode 'emacs))) +@end lisp + +@node @code{define-record-type*} Reference +@subsection @code{define-record-type*} Reference +@defmac define-record-type* name syntactic-constructor constructor predicate this-identifier fields ... + +Define a new record type and associated helpers. + +@table @var +@item name +A symbol used to name the type, as would normally be provided to a plain +@code{define-record-type} form. For example, @code{}. + +@item syntactic-constructor +A symbol that will be used to define the user-facing constructor. For example, +the symbol @code{package} is the syntactic constructor for the @code{} +structure. + +@item constructor +A symbol that will be used to define the traditional constructor. It is used in +the implementation of the syntactic constructor, but will not typically be used +elsewhere. The traditional @code{make-name} (for example, @code{make-package}) +is a fine value to use here. + +@item predicate +A symbol that will be used to test if a value is an instance of this record. +For example, @code{package?}. + +@item this-identifier +This symbol can be used when defining fields that need to refer to the struct +that contains them. For an example of this, see the @code{thunked} field +property, below. + +@item fields +A set of field specifiers which take the following form: + +@lisp +(field-name field-getter properties ...) +@end lisp + +Each of the properties must have one of the following forms: + +@table @code +@item (default @var{value}) +Defines the default value for the field, if the user does not specify one using +the syntactic constructor. + +@item (innate) +Fields marked as innate will not be inherited from parent objects (see +Instantiating Records, below, for details of object inheritance). + +@item (sanitize @var{proc}) +The value given by the user will be passed into @var{proc} before being stored +in the object. For example, consider this struct definition: + +@lisp +(define-record-type* thing make-thing +  thing? +  this-thing +  (name  thing-name +         (sanitize (lambda (value) +                     (cond ((string? value) value) +                           ((symbol? value) (symbol->string value)) +                           (else (throw 'bad! value))))))) +@end lisp + +When creating @code{thing} instances either a string or a symbol can be +supplied but it will always be stored as a string: + +@lisp +(string? (thing-name (thing (name "some-name")))) +@result{} #t +(string? (thing-name (thing (name 'some-name)))) +@result{} #t +(thing (name 1994)) +@result{} Throw to key `bad!' with args `(1994)'. +@end lisp + +@item (thunked) +Fields marked as @code{thunked} will actually compute the field's value in the +current dynamic extent which is useful when referring to fluids in a field's +value. Furthermore, that thunk can access the record it belongs to via the +@code{this-identifier}. For example: + +@lisp +(define-record-type* rectangle make-rectangle +  rectangle? +  this-rectangle +  (width  rectangle-width) +  (height rectangle-height) +  (area rectangle-area (thunked) +                       (default (* (rectangle-width this-rectangle) +                                   (rectangle-height this-rectangle))))) + +(define base-rectangle +  (rectangle +    (width  2) +    (height 4))) +