diff options
| author | Paul Eggert <eggert@cs.ucla.edu> | 2015-03-24 11:42:53 -0700 |
|---|---|---|
| committer | Paul Eggert <eggert@cs.ucla.edu> | 2015-03-24 11:43:21 -0700 |
| commit | 711770da9101a94ada42881cb86a976d323e9348 (patch) | |
| tree | 71465e72be54b14ec973cbf50a4a424449b31a07 | |
| parent | 1e043f5e79bf67c9ebfa35623edcff0633d37a75 (diff) | |
Fix minor ldexp issues
* doc/lispref/numbers.texi (Float Basics): Improve ldexp documentation.
* src/floatfns.c (Fldexp): Require 2 args. Avoid undefined behavior
if the exponent is out of 'int' range. Improve documentation.
Fixes: bug#20185
| -rw-r--r-- | doc/lispref/ChangeLog | 4 | ||||
| -rw-r--r-- | doc/lispref/numbers.texi | 12 | ||||
| -rw-r--r-- | src/ChangeLog | 7 | ||||
| -rw-r--r-- | src/floatfns.c | 10 |
4 files changed, 25 insertions, 8 deletions
diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog index a546306f9e..9b1bbb357a 100644 --- a/doc/lispref/ChangeLog +++ b/doc/lispref/ChangeLog @@ -1,3 +1,7 @@ +2015-03-24 Paul Eggert <eggert@cs.ucla.edu> + + * numbers.texi (Float Basics): Improve ldexp documentation. + 2015-03-23 Eli Zaretskii <eliz@gnu.org> * commands.texi (Event Input Misc): Fix incorrect usage of @code. diff --git a/doc/lispref/numbers.texi b/doc/lispref/numbers.texi index 8d1d3a798e..7b4a0a6d40 100644 --- a/doc/lispref/numbers.texi +++ b/doc/lispref/numbers.texi @@ -265,9 +265,15 @@ If @var{x} is a NaN, then @var{s} is also a NaN@. If @var{x} is zero, then @var{e} is 0. @end defun -@defun ldexp sig &optional exp -This function returns a floating-point number corresponding to the -significand @var{sig} and exponent @var{exp}. +@defun ldexp s e +Given a numeric significand @var{s} and an integer exponent @var{e}, +this function returns the floating point number +@ifnottex +@var{s} * 2**@var{e}. +@end ifnottex +@tex +@math{s 2^e}. +@end tex @end defun @defun copysign x1 x2 diff --git a/src/ChangeLog b/src/ChangeLog index 815c117308..23f125c567 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,3 +1,10 @@ +2015-03-24 Paul Eggert <eggert@cs.ucla.edu> + + Fix minor ldexp issues + * floatfns.c (Fldexp): Require 2 args. Avoid undefined behavior + if the exponent is out of 'int' range. Improve documentation. + Fixes: bug#20185 + 2015-03-24 Daniel Colascione <dancol@dancol.org> * process.c (Fprocess_running_child_p): Return number identifier of diff --git a/src/floatfns.c b/src/floatfns.c index c68b9bd3a6..072e85776b 100644 --- a/src/floatfns.c +++ b/src/floatfns.c @@ -185,14 +185,14 @@ If X is zero, both parts (SGNFCAND and EXP) are zero. */) return Fcons (make_float (sgnfcand), make_number (exponent)); } -DEFUN ("ldexp", Fldexp, Sldexp, 1, 2, 0, - doc: /* Construct number X from significand SGNFCAND and exponent EXP. -Returns the floating point value resulting from multiplying SGNFCAND -(the significand) by 2 raised to the power of EXP (the exponent). */) +DEFUN ("ldexp", Fldexp, Sldexp, 2, 2, 0, + doc: /* Return X * 2**EXP, as a floating point number. +EXP must be an integer. */) (Lisp_Object sgnfcand, Lisp_Object exponent) { CHECK_NUMBER (exponent); - return make_float (ldexp (XFLOATINT (sgnfcand), XINT (exponent))); + int e = min (max (INT_MIN, XINT (exponent)), INT_MAX); + return make_float (ldexp (XFLOATINT (sgnfcand), e)); } DEFUN ("exp", Fexp, Sexp, 1, 1, 0, |