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Fix minor ldexp issues

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* 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
This commit is contained in:
Paul Eggert 2015-03-24 11:42:53 -07:00
parent 1e043f5e79
commit 711770da91
4 changed files with 25 additions and 8 deletions
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4
doc/lispref/ChangeLog
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@ -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.

12
doc/lispref/numbers.texi
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@ -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

7
src/ChangeLog
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@ -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

10
src/floatfns.c
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@ -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,