Front page | perl.perl5.porters |
Postings from November 2000
On Fri, Nov 24, 2000 at 08:18:07PM -0600, Jarkko Hietaniemi wrote:
> On Fri, Nov 24, 2000 at 09:51:39PM +0000, Nicholas Clark wrote:
> > PS I don't like floating point numbers. printf can give you numbers such as
> > NaN and Infinity, so why can't scanf read 'em? :-(
>
> I've been lately adding such intelligence to lexing, e.g. 'Inf' is now
> recognized as a number and atof() is applied on it. The problem is
nick@Bagpuss [bleadperl-intops]$ perl -wle 'print "infinity" + 1'
Argument "infinity" isn't numeric in addition (+) at -e line 1.
inf
nick@Bagpuss [bleadperl-intops]$ perl -wle 'print "inf" + 1'
inf
--- sv.c.orig Wed Nov 22 23:58:27 2000
+++ sv.c Sat Nov 25 22:34:57 2000
@@ -2010,6 +2010,7 @@
s++; if (*s != 'I' && *s != 'i') return 0;
s++; if (*s != 'T' && *s != 't') return 0;
s++; if (*s != 'Y' && *s != 'y') return 0;
+ s++;
}
sawinf = 1;
}
voila:
nick@Bagpuss [bleadperl]$ perl -le 'print "infinity" + 1'
inf
all regression tests still pass
no idea where the regression tests for these warnings should go.
> that there is no portable way to safely produced NaN and Infs... it
> may be that atof() doesn't recognize 'Inf'? (I had a very frustrating
Sorry, it was an expression of my general dislike of floating point,
following my experience with C & C++ parsing files. And the way that
C was happy to output a "number" that it didn't accept as a "number"
on input. I'm not suggesting that the C spec is wrong, just that life
is frustrating when there's not a round trip (via a file) available for
all possible values a float or double holds.
Anyway, glibc seems to like NaN and infinity:
nick@Bagpuss [bleadperl]$ perl -wle 'print "nan" * 0'
Argument "nan" isn't numeric in multiplication (*) at -e line 1.
nan
nick@Bagpuss [bleadperl]$ perl -wle 'print "control" * 0'
Argument "control" isn't numeric in multiplication (*) at -e line 1.
0
FreeBSD doesn't:
bash-2.02$ perl -wle 'print "nan" * 0'
Argument "nan" isn't numeric in multiply at -e line 1.
0
bash-2.02$ ./perl -wle 'print "inf" + 1'
1
bash-2.02$ ./perl -wle 'print "infinity" + 1'
1
Nicholas Clark
Thread Previous
|
Thread Next