50 lines
1.3 KiB
EmacsLisp
50 lines
1.3 KiB
EmacsLisp
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;;; dotted.el --- Working with dotted pairs in Elisp -*- lexical-binding: t -*-
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;; Author: William Carroll <wpcarro@gmail.com>
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;;; Commentary:
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;; Part of my primitives library extensions in Elisp. Contrast my primitives
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;; with the wrapper extensions that I provide, which expose immutable variants
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;; of data structures like an list, alist, tuple, as well as quasi-typeclasses
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;; like sequence, etc.
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;;; Code:
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(require 'prelude)
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(require 'macros)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Library
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(cl-defun dotted/new (&optional a b)
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"Create a new dotted pair (i.e. cons cell)."
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(cons a b))
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(defun dotted/instance? (x)
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"Return t if X is a dotted pair."
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(let ((b (cdr x)))
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(and b (atom b))))
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(defun dotted/first (x)
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"Return the first element of X."
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(car x))
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(defun dotted/second (x)
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"Return the second element of X."
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(cdr x))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Tests
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(progn
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(prelude/assert
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(equal '(fname . "Bob") (dotted/new 'fname "Bob")))
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(prelude/assert
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(dotted/instance? '(one . two)))
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(prelude/refute
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(dotted/instance? '(1 2 3))))
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(provide 'dotted)
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;;; dotted.el ends here
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