ID: 10351
Updated by: [EMAIL PROTECTED]
Reported By: dwilson at cae dot wisc dot edu
-Status: Open
+Status: Closed
Bug Type: Documentation problem
Operating System: Sun OS 5.7
PHP Version: 4.0.3pl1
New Comment:
This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.
Thank you for the report, and for helping us make our documentation
better.
Previous Comments:
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[2002-04-29 13:12:00] m dot ford at lmu dot ac dot uk
I think the key here is not precedence, but associativity. The ?:
operator is listed as being left-associative which, I think, means your
simplified example will be evaluated like this:
(1 ? (1 ? "3" : "2") : 1) ? "1" : "0"
which will, indeed, result in 1!
A right-associative ?: would be grouped as you expected, like this:
1 ? (1 ? "3" : "2") : (1 ? "1" : "0")
-- ergo, in C ?: must be right-associative!!
(As a side-note, operator associativity is listed in the operator
precedence table with no real explanation of what it means, or link to
such explanation -- perhaps this should be made a documentation feature
request?)
------------------------------------------------------------------------
[2002-04-29 10:34:57] dwilson at cae dot wisc dot edu
I checked, and < has a higher precedence than ?: as one
would expect. For example, with $dHour = 5, this is
equivalent to:
$departmeals = 1 ? 1 ? "3" : "2" : 1 ? "1" : "0";
which should evaluate to "3" but evaluates to "1" instead.
The C language has no trouble with this construction:
sun-66% cat temp.c
#include <stdio.h>
main(){
printf("%s\n",1 ? 1 ? "3" : "2" : 1 ? "1" : "0");
}
sun-66% cc temp.c
sun-66% a.out
3
------------------------------------------------------------------------
[2002-04-27 15:19:22] [EMAIL PROTECTED]
it does execute correctly, given the relative precedence of the '<' and
'?:' operators.
------------------------------------------------------------------------
[2001-04-16 16:14:48] dwilson at cae dot wisc dot edu
The following statement does not execute correctly:
$departmeals = $dHour < 10.5 ? $dHour < 6.0 ? "3" : "2"
:
$dHour < 18.0 ? "1" : "0";
No error message--it just returns the wrong result. It does execute
correctly if parentheses are added:
$departmeals = $dHour < 10.5 ? ($dHour < 6.0 ? "3" : "2")
:
($dHour < 18.0 ? "1" : "0");
The original is not ambiguous; it should parse and execute correctly.
------------------------------------------------------------------------
--
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