Doc->Bug #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: yohgaki@php.net Reported by: cmbecker69 at gmx dot de -Summary: Comma operator has insufficient documentation +Summary: Comma operator does not behave as operator Status: Open -Type: Documentation Problem +Type: Bug -Package: Documentation problem +Package: Scripting Engine problem Operating System: * PHP Version: Irrelevant Block user comment: N Private report: N New Comment: Reasonable discussion. Since this is documented for a long time, it may be good to categorize as engine issue. Previous Comments: ------------------------------------------------------------------------ [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