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 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: internal
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;;; Code:
  28
  29 ;; Provide a meaningful error message if we are running on
  30 ;; bare (non-float) emacs.
  31
  32 (if (fboundp 'atan)
  33     nil
  34   (error "Floating point was disabled at compile time"))
  35
  36 ;; provide an easy hook to tell if we are running with floats or not.
  37 ;; define pi and e via math-lib calls. (much less prone to killer typos.)
  38 (defconst pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")
  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 ;; Careful when editing this file ... typos here will be hard to spot.
  44 ;; (defconst pi       3.14159265358979323846264338327
  45 ;;  "The value of Pi (3.14159265358979323846264338327...)")
  46
  47 (defconst degrees-to-radians (/ pi 180.0)
  48   "Degrees to radian conversion constant.")
  49 (defconst radians-to-degrees (/ 180.0 pi)
  50   "Radian to degree conversion constant.")
  51
  52 ;; these expand to a single multiply by a float when byte compiled
  53
  54 (defmacro degrees-to-radians (x)
  55   "Convert ARG from degrees to radians."
  56   (list '* (/ pi 180.0) x))
  57 (defmacro radians-to-degrees (x)
  58   "Convert ARG from radians to degrees."
  59   (list '* (/ 180.0 pi) x))
  60
  61 (provide 'lisp-float-type)
  62
  63 ;;; arch-tag: e7837072-a4af-4d08-9953-8a3e755abf9d
  64 ;;; float-sup.el ends here