lisp/emacs-lisp/float-sup.el

   1 ;;; float-sup.el --- define some constants useful for floating point numbers.
   2
   3 ;; Copyright (C) 1985, 1986, 1987, 2001, 2002, 2003, 2004,
   4 ;;   2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   5
   6 ;; Maintainer: FSF
   7 ;; Keywords: internal
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software: you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation, either version 3 of the License, or
  14 ;; (at your option) any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;;; Code:
  27
  28 ;; Provide a meaningful error message if we are running on
  29 ;; bare (non-float) emacs.
  30
  31 (if (fboundp 'atan)
  32     nil
  33   (error "Floating point was disabled at compile time"))
  34
  35 ;; provide an easy hook to tell if we are running with floats or not.
  36 ;; define pi and e via math-lib calls. (much less prone to killer typos.)
  37 (defconst pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")
  38
  39 ;; It's too inconvenient to make `e' a constant because it's used as
  40 ;; a temporary variable all the time.
  41 (defvar e (exp 1) "The value of e (2.7182818...).")
  42
  43 (defconst degrees-to-radians (/ pi 180.0)
  44   "Degrees to radian conversion constant.")
  45 (defconst radians-to-degrees (/ 180.0 pi)
  46   "Radian to degree conversion constant.")
  47
  48 ;; these expand to a single multiply by a float when byte compiled
  49
  50 (defmacro degrees-to-radians (x)
  51   "Convert ARG from degrees to radians."
  52   (list '* (/ pi 180.0) x))
  53 (defmacro radians-to-degrees (x)
  54   "Convert ARG from radians to degrees."
  55   (list '* (/ 180.0 pi) x))
  56
  57 (provide 'lisp-float-type)
  58
  59 ;; arch-tag: e7837072-a4af-4d08-9953-8a3e755abf9d
  60 ;;; float-sup.el ends here