578ed1ba98
Moving all of my Emacs-related files into their own directory at the root of this repository.
88 lines
3.1 KiB
EmacsLisp
88 lines
3.1 KiB
EmacsLisp
;;; struct.el --- Helpers for working with structs -*- lexical-binding: t -*-
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;; Author: William Carroll <wpcarro@gmail.com>
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;;; Commentary:
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;; Provides new macros for working with structs. Also provides adapter
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;; interfaces to existing struct macros, that should have more intuitive
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;; interfaces.
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;;
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;; Sometimes `setf' just isn't enough.
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;;; Code:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Wish list
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; - TODO: Replace `symbol-name' and `intern' calls with isomorphism.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Dependencies
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(require 'string)
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(require 'dash)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Library
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(defvar struct/enable-tests? t
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"When t, run the test suite defined herein.")
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(defmacro struct/update (type field f xs)
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"Apply F to FIELD in XS, which is a struct of TYPE.
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This is immutable."
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(let ((copier (->> type
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symbol-name
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(string/prepend "copy-")
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intern))
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(accessor (->> field
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symbol-name
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(string/prepend (string/concat (symbol-name type) "-"))
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intern)))
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`(let ((copy (,copier ,xs)))
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(setf (,accessor copy) (funcall ,f (,accessor copy)))
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copy)))
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(defmacro struct/set (type field x xs)
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"Immutably set FIELD in XS (struct TYPE) to X."
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(let ((copier (->> type
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symbol-name
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(string/prepend "copy-")
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intern))
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(accessor (->> field
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symbol-name
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(string/prepend (string/concat (symbol-name type) "-"))
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intern)))
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`(let ((copy (,copier ,xs)))
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(setf (,accessor copy) ,x)
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copy)))
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(defmacro struct/set! (type field x xs)
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"Set FIELD in XS (struct TYPE) to X mutably.
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This is an adapter interface to `setf'."
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(let ((accessor (->> field
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symbol-name
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(string/prepend (string/concat (symbol-name type) "-"))
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intern)))
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`(progn
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(setf (,accessor ,xs) ,x)
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,xs)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Tests
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(when struct/enable-tests?
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(cl-defstruct dummy name age)
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(defvar test-dummy (make-dummy :name "Roofus" :age 19))
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(struct/set! dummy name "Doofus" test-dummy)
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(prelude/assert (string= "Doofus" (dummy-name test-dummy)))
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(let ((result (struct/set dummy name "Shoofus" test-dummy)))
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;; Test the immutability of `struct/set'
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(prelude/assert (string= "Doofus" (dummy-name test-dummy)))
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(prelude/assert (string= "Shoofus" (dummy-name result)))))
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(provide 'struct)
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;;; struct.el ends here
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