From: Bernard Hurley <bernard@marcade.biz>
To: 20185@debbugs.gnu.org
Subject: bug#20185: 24.4.50; problem with built-in function "ldexp" Emacs Ver: 24.4.50.1
Date: Mon, 23 Mar 2015 20:29:13 +0000 [thread overview]
Message-ID: <87y4mn4fvq.fsf@snares-penguin.marcade.biz> (raw)
(24.4.50) 3.2 Floating-Point Basics we read:
---------- snip ------------
-- Function: ldexp sig &optional exp
This function returns a floating-point number corresponding to the
significand SIG and exponent EXP.
----------snip -------------
However it is easy to verify that the second argument is not
optional. For example:
(ldexp 5.0)
triggers the error:
*** Eval error *** Wrong type argument: integerp, nil
The code for ldexp in floatfn.c reads:
---------- snip ---------------
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). */)
(Lisp_Object sgnfcand, Lisp_Object exponent)
{
CHECK_NUMBER (exponent);
return make_float (ldexp (XFLOATINT (sgnfcand), XINT (exponent)));
}
---------- snip -------------
The declaration conforms to that in the manual but nothing seems to have
been done to take into account what happens when `exp' is missing. It
seems to me that there are two possibilities:
EITHER: The declaration in floatfns.c is incorrect and should read:
DEFUN ("ldexp", Fldexp, Sldexp, 1, 1, 0,
....
In which case it will need to be changed and the manual will need to be
changed accordingly.
OR: `exp' is supposed to have a default value (0 say), when the code in
floatfns.c should be changed accordingly. In this case it might still
be a good idea to update the manual to explain that it has this value.
next reply other threads:[~2015-03-23 20:29 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-23 20:29 Bernard Hurley [this message]
2015-03-24 18:57 ` bug#20185: 24.4.50; problem with built-in function "ldexp" Emacs Ver: 24.4.50.1 Paul Eggert
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