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comparison man/lispref/numbers.texi @ 280:7df0dd720c89 r21-0b38

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Import from CVS: tag r21-0b38
author cvs
date Mon, 13 Aug 2007 10:32:22 +0200
parents 65c19d2020f7
children
comparison
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279:c20b2fb5bb0a 280:7df0dd720c89
238 exact, it is often a bad idea to check for equality of two floating 238 exact, it is often a bad idea to check for equality of two floating
239 point values. Usually it is better to test for approximate equality. 239 point values. Usually it is better to test for approximate equality.
240 Here's a function to do this: 240 Here's a function to do this:
241 241
242 @example 242 @example
243 (defvar fuzz-factor 1.0e-6) 243 (defconst fuzz-factor 1.0e-6)
244 (defun approx-equal (x y) 244 (defun approx-equal (x y)
245 (or (and (= x 0) (= y 0)) 245 (or (and (= x 0) (= y 0))
246 (< (/ (abs (- x y)) 246 (< (/ (abs (- x y))
247 (max (abs x) (abs y))) 247 (max (abs x) (abs y)))
248 fuzz-factor))) 248 fuzz-factor)))
255 distinct integer objects can have the same numeric value. XEmacs Lisp 255 distinct integer objects can have the same numeric value. XEmacs Lisp
256 can have just one integer object for any given value because it has a 256 can have just one integer object for any given value because it has a
257 limited range of integer values. 257 limited range of integer values.
258 @end quotation 258 @end quotation
259 259
260 @defun = number-or-marker1 number-or-marker2 260 In addition to numbers, all of the following functions also accept
261 This function tests whether its arguments are numerically equal, and 261 characters and markers as arguments, and treat them as their number
262 returns @code{t} if so, @code{nil} otherwise. 262 equivalents.
263 @end defun 263
264 264 @defun = number &rest more-numbers
265 @defun /= number-or-marker1 number-or-marker2 265 This function returns @code{t} if all of its arguments are numerically
266 This function tests whether its arguments are numerically not equal. It 266 equal, @code{nil} otherwise.
267 returns @code{t} if so, and @code{nil} otherwise. 267
268 @end defun 268 @example
269 269 (= 5)
270 @defun < number-or-marker1 number-or-marker2 270 @result{} t
271 This function tests whether its first argument is strictly less than 271 (= 5 6)
272 its second argument. It returns @code{t} if so, @code{nil} otherwise. 272 @result{} nil
273 @end defun 273 (= 5 5.0)
274 274 @result{} t
275 @defun <= number-or-marker1 number-or-marker2 275 (= 5 5 6)
276 This function tests whether its first argument is less than or equal 276 @result{} nil
277 to its second argument. It returns @code{t} if so, @code{nil} 277 @end example
278 otherwise. 278 @end defun
279 @end defun 279
280 280 @defun /= number &rest more-numbers
281 @defun > number-or-marker1 number-or-marker2 281 This function returns @code{t} if no two arguments are numerically
282 This function tests whether its first argument is strictly greater 282 equal, @code{nil} otherwise.
283 than its second argument. It returns @code{t} if so, @code{nil} 283
284 otherwise. 284 @example
285 @end defun 285 (/= 5 6)
286 286 @result{} t
287 @defun >= number-or-marker1 number-or-marker2 287 (/= 5 5 6)
288 This function tests whether its first argument is greater than or 288 @result{} nil
289 equal to its second argument. It returns @code{t} if so, @code{nil} 289 (/= 5 6 1)
290 otherwise. 290 @result{} t
291 @end defun 291 @end example
292 292 @end defun
293 @defun max number-or-marker &rest numbers-or-markers 293
294 @defun < number &rest more-numbers
295 This function returns @code{t} if the sequence of its arguments is
296 monotonically increasing, @code{nil} otherwise.
297
298 @example
299 (< 5 6)
300 @result{} t
301 (< 5 6 6)
302 @result{} nil
303 (< 5 6 7)
304 @result{} t
305 @end example
306 @end defun
307
308 @defun <= number &rest more-numbers
309 This function returns @code{t} if the sequence of its arguments is
310 monotonically nondecreasing, @code{nil} otherwise.
311
312 @example
313 (<= 5 6)
314 @result{} t
315 (<= 5 6 6)
316 @result{} t
317 (<= 5 6 5)
318 @result{} nil
319 @end example
320 @end defun
321
322 @defun > number &rest more-numbers
323 This function returns @code{t} if the sequence of its arguments is
324 monotonically decreasing, @code{nil} otherwise.
325 @end defun
326
327 @defun >= number &rest more-numbers
328 This function returns @code{t} if the sequence of its arguments is
329 monotonically nonincreasing, @code{nil} otherwise.
330 @end defun
331
332 @defun max number &rest more-numbers
294 This function returns the largest of its arguments. 333 This function returns the largest of its arguments.
295 334
296 @example 335 @example
297 (max 20) 336 (max 20)
298 @result{} 20 337 @result{} 20
301 (max 1 3 2.5) 340 (max 1 3 2.5)
302 @result{} 3 341 @result{} 3
303 @end example 342 @end example
304 @end defun 343 @end defun
305 344
306 @defun min number-or-marker &rest numbers-or-markers 345 @defun min number &rest more-numbers
307 This function returns the smallest of its arguments. 346 This function returns the smallest of its arguments.
308 347
309 @example 348 @example
310 (min -4 1) 349 (min -4 1)
311 @result{} -4 350 @result{} -4