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63 lines
2.1 KiB
EmacsLisp
63 lines
2.1 KiB
EmacsLisp
;;; float-sup.el --- define some constants useful for floating point numbers.
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;; Copyright (C) 1985, 1986, 1987, 2001, 2002, 2003, 2004,
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;; 2005, 2006, 2007 Free Software Foundation, Inc.
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;; Maintainer: FSF
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;; Keywords: internal
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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;; Boston, MA 02110-1301, USA.
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;;; Commentary:
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;;; Code:
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;; Provide a meaningful error message if we are running on
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;; bare (non-float) emacs.
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(if (fboundp 'atan)
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nil
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(error "Floating point was disabled at compile time"))
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;; provide an easy hook to tell if we are running with floats or not.
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;; define pi and e via math-lib calls. (much less prone to killer typos.)
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(defconst pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")
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;; It's too inconvenient to make `e' a constant because it's used as
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;; a temporary variable all the time.
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(defvar e (exp 1) "The value of e (2.7182818...).")
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(defconst degrees-to-radians (/ pi 180.0)
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"Degrees to radian conversion constant.")
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(defconst radians-to-degrees (/ 180.0 pi)
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"Radian to degree conversion constant.")
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;; these expand to a single multiply by a float when byte compiled
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(defmacro degrees-to-radians (x)
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"Convert ARG from degrees to radians."
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(list '* (/ pi 180.0) x))
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(defmacro radians-to-degrees (x)
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"Convert ARG from radians to degrees."
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(list '* (/ 180.0 pi) x))
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(provide 'lisp-float-type)
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;;; arch-tag: e7837072-a4af-4d08-9953-8a3e755abf9d
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;;; float-sup.el ends here
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