ID: 40996
Updated by: [EMAIL PROTECTED]
Reported By: ehanneken at pobox dot com
Status: Open
Bug Type: Documentation problem
PHP Version: Irrelevant
New Comment:
I wonder whether or not we should have the formal grammar at all. We're
not trying to teach people how to parse floating point numbers: just
tell them how to write them out. Plus, it's not even stated what the
grammar is written in! (it's certainly not EBNF, not a Perl regexp due
to extra spacing, what is it?)
The formal grammar was added by jeroen in v1.21 as a comment, which
goba turned into an actual section later on.
The PHP parser doesn't "natively" recognize signs to the float syntax:
so +-+-+-+3.4, while very strange, does work with the PHP parser.
Instead, we're really using + and - operator to change the sign of the
float. I.e.
-4.2 == -(4.2) to the PHP parser
For the average Joe, I don't think this distinction makes much
difference though.
Finally, the revised grammar has a bug: it doesn't include "unsigned"
exponential non-decimal numbers, eg. 4e4.
Previous Comments:
------------------------------------------------------------------------
[2007-04-04 15:03:32] ehanneken at pobox dot com
There was a bug in my revised grammar, too. How about this?
ULNUM [0-9]+
SLNUM [+-]{ULNUM}
DNUM [+-]?(([0-9]*[\.]{ULNUM}) | ({ULNUM}[\.][0-9]*))
EXPONENT_DNUM ( ({SLNUM} | {DNUM}) [eE][+-]? {ULNUM})
------------------------------------------------------------------------
[2007-04-04 15:03:12] ehanneken at pobox dot com
There was a bug in my revised grammer, too. How about this?
ULNUM [0-9]+
SLNUM [+-]{ULNUM}
DNUM [+-]?(([0-9]*[\.]{ULNUM}) | ({ULNUM}[\.][0-9]*))
EXPONENT_DNUM ( ({SLNUM} | {DNUM}) [eE][+-]? {ULNUM})
------------------------------------------------------------------------
[2007-04-04 14:56:00] ehanneken at pobox dot com
Description:
------------
According to the manual
(http://www.php.net/manual/en/language.types.float.php), the following
grammar specifies floating point numbers:
LNUM [0-9]+
DNUM ([0-9]*[\.]{LNUM}) | ({LNUM}[\.][0-9]*)
EXPONENT_DNUM ( ({LNUM} | {DNUM}) [eE][+-]? {LNUM})
This leaves out signed numbers. The grammar should be written as
something like
ULNUM [0-9]+
SLNUM [+-]{ULNUM}
DNUM [+-]?(([0-9]*[\.]{ULNUM}) | ({ULNUM}[\.][0-9]*))
EXPONENT_DNUM [+-]?( ({ULNUM} | {DNUM}) [eE][+-]? {ULNUM})
Reproduce code:
---------------
echo gettype(-3.14) . "\n";
echo gettype(+3.14);
Expected result:
----------------
double
double
Actual result:
--------------
double
double
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=40996&edit=1
