Bug->Doc #66772 [Opn]: Comma operator does not behave as operator

Edit report at https://bugs.php.net/bug.php?id=66772&edit=1 ID: 66772 Updated by: nikic@php.net Reported by: cmbecker69 at gmx dot de Summary: Comma operator does not behave as operator Status: Open -Type: Bug +Type: Documentation Problem -Package: Scripting Engine problem +Package: Documentation problem Operating System: * PHP Version: Irrelevant Block user comment: N Private report: N New Comment: @yasuo: This is docs problem. PHP has no comma operator, it only uses commas as an expression delimiter in some places, like function arguments. Previous Comments: ------------------------------------------------------------------------ [2014-07-07 11:44:07] cmbecker69 at gmx dot de > Since this is documented for a long time, it may be good to > categorize as engine issue. Please note, that I do not suggest to implement a universal comma operator as in C/C++. Actually, I believe that it is not necessary and doesn't have real benefits (at least in PHP). IMHO it would be sufficient to document the comma operator more clearly, or perhaps, to not categorize it as *operator* at all (Java does not have a comma operator[1], but similar uses of the comma as in PHP). [1] <http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.27-120> ------------------------------------------------------------------------ [2014-07-07 05:38:16] yohgaki@php.net Reasonable discussion. Since this is documented for a long time, it may be good to categorize as engine issue. ------------------------------------------------------------------------ [2014-07-06 10:52:38] cmbecker69 at gmx dot de > I think ',' is used to divide expressions just like C/C++, > isn't? It doesn't seem to be in the general case. For instance: $a = (1, 2); // => syntax error, unexpected ',' Furthermore in C the comma operator doesn't simply divide expressions, but is defined to evaluate the first operand discarding the result, and than to evaluate the second operand "returning" its result. > echo 1,2,3,4; This is possible due to the special grammar rule echo_expr_list. > I'm not sure what do you mean by "the operator precedence table > seems to be in error." The *only* case where the comma can be used as *operator* seems to be inside for_expr. However, the documentation states the comma operator has *many* uses. ------------------------------------------------------------------------ [2014-07-06 02:52:11] yohgaki@php.net I think ',' is used to divide expressions just like C/C++, isn't? Therefore, echo 1,2,3,4; as well as $i=0; echo ++$i, ++$i, ++$i; works. http://en.cppreference.com/w/cpp/language/operator_precedence http://www.difranco.net/compsci/C_Operator_Precedence_Table.htm I'm not sure what do you mean by "the operator precedence table seems to be in error." ------------------------------------------------------------------------ [2014-02-25 20:35:18] cmbecker69 at gmx dot de Description: ------------ The section "Operator Precedence"[1] lists all operators and gives a link to the manual section where they are described; for the comma operator it only says "many uses". It seems to be appropriate to list these many uses in an own section. OTOH, from what I can tell from Zend/zend_language_parser.y[2] the only actual place where the comma is used as operator (opposed to a list delimiter) is inside for_expr. This usage is explained in the "for" section[3]. If this is indeed the only use, the operator precendence table seems to be in error. [1] <http://www.php.net/manual/en/language.operators.precedence.php> [2] <http://lxr.php.net/xref/PHP_5_5/Zend/zend_language_parser.y> [3] <http://www.php.net/manual/en/control-structures.for.php> ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=66772&edit=1