578ed1ba98
Moving all of my Emacs-related files into their own directory at the root of this repository.
86 lines
2.3 KiB
EmacsLisp
86 lines
2.3 KiB
EmacsLisp
;;; tuple.el --- Tuple API for Elisp -*- lexical-binding: t -*-
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;; Author: William Carroll <wpcarro@gmail.com>
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;;; Commentary:
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;; Work with cons cells with two elements with a familiar API for those who have
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;; worked with tuples before.
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;;; Code:
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(cl-defstruct tuple first second)
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;; Create
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(defun tuple/new ()
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"Return an empty tuple."
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(make-tuple :first nil
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:second nil))
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(defun tuple/from (a b)
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"Return a new tuple from A and B."
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(make-tuple :first a
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:second b))
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(defun tuple/from-dotted (dp)
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"Convert dotted pair, DP, into a tuple."
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(tuple/from (car dp) (cdr dp)))
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;; Read
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(defun tuple/first (pair)
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"Return the first element of PAIR."
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(tuple-first pair))
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(defun tuple/second (pair)
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"Return the second element of PAIR."
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(tuple-second pair))
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;; Update
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(defun tuple/map-each (f g pair)
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"Apply F to first, G to second in PAIR."
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(->> pair
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(tuple/map-first f)
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(tuple/map-second g)))
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(defun tuple/map (f pair)
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"Apply F to PAIR."
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(let ((pair-copy (copy-tuple pair)))
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(funcall f pair-copy)))
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(defun tuple/map-first (f pair)
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"Apply function F to the first element of PAIR."
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(let ((pair-copy (copy-tuple pair)))
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(setf (tuple-first pair-copy) (funcall f (tuple/first pair-copy)))
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pair-copy))
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(defun tuple/map-second (f pair)
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"Apply function F to the second element of PAIR."
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(let ((pair-copy (copy-tuple pair)))
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(setf (tuple-second pair-copy) (funcall f (tuple/second pair-copy)))
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pair-copy))
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(defun tuple/set-first (a pair)
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"Return a new tuple with the first element set as A in PAIR."
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(tuple/map-first (lambda (_) a) pair))
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(defun tuple/set-second (b pair)
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"Return a new tuple with the second element set as B in PAIR."
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(tuple/map-second (lambda (_) b) pair))
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;; Delete
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(defun tuple/delete-first (pair)
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"Return PAIR with the first element set to nil."
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(tuple/set-first nil pair))
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(defun tuple/delete-second (pair)
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"Return PAIR with the second element set to nil."
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(tuple/set-second nil pair))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Predicates
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(defun tuple/instance? (x)
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"Return t if X is a tuple."
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(tuple-p x))
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(provide 'tuple)
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;;; tuple.el ends here
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