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 ;; Package: emacs
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  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
  40 ;; It's too inconvenient to make `e' a constant because it's used as
  41 ;; a temporary variable all the time.
  42 (defvar e (exp 1) "The value of e (2.7182818...).")
  43
  44 (defconst degrees-to-radians (/ pi 180.0)
  45   "Degrees to radian conversion constant.")
  46 (defconst radians-to-degrees (/ 180.0 pi)
  47   "Radian to degree conversion constant.")
  48
  49 ;; these expand to a single multiply by a float when byte compiled
  50
  51 (defmacro degrees-to-radians (x)
  52   "Convert ARG from degrees to radians."
  53   (list '* (/ pi 180.0) x))
  54 (defmacro radians-to-degrees (x)
  55   "Convert ARG from radians to degrees."
  56   (list '* (/ 180.0 pi) x))
  57
  58 (provide 'lisp-float-type)
  59
  60 ;; arch-tag: e7837072-a4af-4d08-9953-8a3e755abf9d
  61 ;;; float-sup.el ends here