On 10/18/2013 3:02 PM, Jim Giner wrote:
On 10/18/2013 10:33 AM, Robert Cummings wrote:
Hi Jim,
I'm not sure it's a bug. There are two considerations... should the
first use of the ternary operator feed the first operand of the second,
or should the second use of the ternary operator feed the 3rd operand of
the first use. Visually... which is more correct:
<?php
$foo = ($a ? $b : $c) ? $d : $e; // PHP does this one.
$foo = $a ? $b : ($c ? $d : $e);
?>
They both seem perfectly reasonable and so I would say it's my job to
clarify if I don't want to leave it the the vagaries of the developer's
subjective opinion :) To me this isn't a flaw in PHP, but an oversight
by the programmer (because they don't see the ambiguity) or they have an
incorrect assumption that one way is the right way. Either way... do you
think the following makes for readable code?
<?php
$foo = $a ? $b : $c ? $d : $e;
?>
Cheers,
Rob.
When I write something like this, I expect it to happen from left to
right. Always have, always will. That said I see the 'proper'
expectation of this statement:
$foo = $a ? $b : $c ? $d : $e;
as:
$foo will be the result of "if $a then $b else if $c then $d else $e;"
Why php interprets it differently is just not logical to me. Of course
writing something like that with one set of parens solves the riddle as
well as making it more readable:
$foo = $a ? $b : ($c ? $d : $e);
As for ambiguity - I don't see it. Again the literal syntax of the
ternary if is (IMHO):
"if (cond) then (statement) else (other statment)"
In your example:
$foo = $a ? $b : $c ? $d : $e;
I see it exactly as this:
"if $a is true then
$b
else
if $c is true then
$d
else
$e;"
Why should php evaluate the last statement before deciding if it even
needs that statement?
And after posting the above and re-reading it several times I can now
see the 'other' interpretation of this puzzle.
Syntactically the ternary operator is recognized by the ? - no?
Therefore the compiler sees that and splits the statement into the three
parts: condition, true result & false result. Call this picture #1.
But in this situation the compiler runs into a second ? and has to
process it a bit differently.
The parts of the concatenation will be condition (picture #1), true
result, & false result.
I guess it's a case of that old expression "the emphasis is on the wrong
syl-lable".
So - while readers of English see it one way, that little old automaton
sees it differently and quite accurately it would seem. I guess the
writers of that compiler never thought about the future confusion it
would raise. Kind of like what I previously mentioned in my earlier
post about less than consistent syntax. This behavior surely is not the
same as the interpretation of a regular old if/then/else with
concatenated if/then/else pieces added in. Would you agree?
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