Req #66368 [Opn]: Operators should also be functions

Edit report at https://bugs.php.net/bug.php?id=66368&edit=1 ID: 66368 Updated by: krakjoe@php.net Reported by: chriswarbo at gmail dot com Summary: Operators should also be functions Status: Open Type: Feature/Change Request Package: *General Issues Operating System: Irrelevant PHP Version: Irrelevant Block user comment: N Private report: N New Comment: I've read this, several times, last night and this morning. I cannot make good sense out of your request, I don't know what you're asking for. Some of this just doesn't make sense (why on earth should [] or -> be a function). I'm sure it all makes sense to you in your head, but I'm having a hard time understanding what it is you want to be implemented. By title alone; you do not want all operators and some language constructs to be functions, that would destroy performance, obviously. You don't appear to want operator overloading because this appears focused on primitive types. What is it exactly that you want ? Sorry if the explanation is there, I just don't see it ... Previous Comments: ------------------------------------------------------------------------ [2013-12-31 10:41:33] chriswarbo at gmail dot com I don't have many examples to hand, since I don't have access to my previous employers' codebases and I've not been at my current job for very long. Here's what a bit of grepping on my current employer's codebase turned up. Here's some array comparison code. "$not_f" is just the composition of "!" and "$f", but we can't compose them directly since "!" is not a function: $sort = function($arr) { sort($arr); return $arr; }; foreach (array('is_null', 'is_bool', 'is_int', 'is_string') as $f) { if (!array_equal($sort(array_filter($array1, $f)), $sort(array_filter($array2, $f)))) return FALSE; $not_f = function($x) use ($f) { return !($f($x)); }; $array1 = array_filter($array1, $not_f); $array2 = array_filter($array2, $not_f); } Note that our codebase already contains the following composition function, but it's utility is massively hampered by so much of PHP's functionality not being in functions: function compose($f, $g) { return function($x) use ($f, $g) { return $f($g($x)); }; } A test case for the compose function contains a few (admittedly artificial) workarounds for PHP's distinction between operators and functions (closing over $a and $b isn't necessary, it just saves us a line or two since PHP doesn't support currying): protected function testComposeComposes() { $a = mt_rand(-1000, 1000); $b = mt_rand(-1000, 1000); $x = mt_rand(-1000, 1000); $f = function($x) use (&$a) { return $x * $a; }; $g = function($x) use (&$b) { return $x + $b; }; $fg = compose($f, $g); $composed = $fg($x); $manual = ($x + $b) * $a; if (!$this->assertIdentical( $composed, $manual, "Composed addition and multiplication $a $b $x $composed $manual")) { $this->dump(array( '$a' => $a, '$b' => $b, '$x' => $x, '$composed' => $composed, '$manual' => $manual )); } } Here's a test method, which again just composes "!" with another function (Drupal's "module_exists" function) but has to do so manually: protected function ourDependenciesAreEnabledTest() { $this->assertTrue( count(array_filter($this->ourDependencies(), function ($m) { return !module_exists($m); })) === 0, 'All of our dependencies are enabled'); } Here's some code for loading all includes from a directory, with a lambda to work around the fact that "require_once" isn't a function: array_map(function($i) { require_once($i); }, find_includes(TRUE)); Here's a version of "array_reduce" which passes the keys to the folding function. The first anonymous function just works around the fact that "array" isn't a function (the second is just an uncurry function): function array_reduce_keys($arr, $f, $i) { return array_reduce( // Pair up keys and values array_map_keys( function ($k, $v) { return array($k, $v); }, $arr), // Pull apart each pair and send to $f function ($result, $pair) use (&$f) { return $f($result, $pair[0], $pair[1]); }, // Start with $i $i); } Here's a test case for the above function, which uses a lambda to work around the fact that "+" isn't a function: protected function testArrayReduceKeysIsGivenKeys() { // Our keys are numeric, so try summing them $arr = $this->randomArray(); $this->assertIdentical( array_sum(array_keys($arr)), array_reduce_keys($arr, function($x, $y, $_) { return $x + $y; }, 0), 'array_reduce_keys is given access to keys'); } Here's a function from our payment system which tries to look up a user's billing information, which is a workaround for "->" not being a function: $default = function($n) use ($billing_info) { return $billing_info->$n; }; Of course, this is code which is in production *despite* PHP's asymmetric treatment of operators and functions. Most of the time I'll refactor the algorithm to work around these deficiencies (manually unrolling maps/folds/filters, hard-coding operators, copy/pasting functions just to change an operator, etc.). Such things are more difficult to grep for than lambdas ("function[ ]*("). Most of the use-cases I found weren't quite applicable, since one of the operator arguments values was constant, for example: function($node) { return 'nodes/' . $node; } function($p, $q) { db_query('UPDATE {quiz_question} SET previous = :p WHERE question_id = :q', array(':p' => $p, ':q' => $q)); } function($x) { return $x? 'right' : 'wrong'; } function ($x) { return abs($x - 1) < 0.0001; } $band_codes = array_map(function($b) { return $b['band']; }, $bands); entity_get_controller('commerce_order')->resetCache( array_map(function($o) { return $o->order_id; }, $orders)); function($key) use ($licensee) { return $licensee[$key]; } function($p) { return product_display_nodes($p->product_id); } With currying and/or partial-application of functions (like the "curry" function at http://chriswarbo.net/data_custom/prelude.txt ), these would become valid use-cases for this ticket, since they would need ".", "array" and "=>", "?!", "<", "[]", and "->" to be functions, respectively. Currying deserves a separate ticket though, and the implementation I linked to isn't intended for production use (PHP doesn't have tail-call optimisation, so I'd need to reign in its stack usage). ------------------------------------------------------------------------ [2013-12-30 20:54:22] anon at anon dot anon >In every project I work on Can you provide even one practical, convincing use case for this feature? ------------------------------------------------------------------------ [2013-12-30 08:32:41] chriswarbo at gmail dot com Oops, $example_1 should use $f not $g. ------------------------------------------------------------------------ [2013-12-30 08:30:35] chriswarbo at gmail dot com Description: ------------ PHP's operators (+, -, *, /, ||, &&, etc.) can be tedious to use, since they are second-class citizens compared to functions. They can't be abstracted (example 1), can't be used as callbacks (example 2) and must be hard-coded (example 3). Operators with non-symbolic names, eg. "or", "and", "xor", etc. can be defined as functions right now without breaking existing code, since their names look like valid functions and are guaranteed to be available (example 4). For consistency, it may be desirable to create synonyms for operators with symbolic names, eg. "+", "-", "*", etc. (example 5). Ambiguities can be handled trivially (example 6). Alternatively, the symbolic names could be used directly (example 7). In every project I work on, I inevitably end up writing these as in-line lambdas, then eventually refactor them out into a library. I'm sure I'm not alone. If PHP stopped treating operators differently from functions, large amounts of boilerplate code could be scrapped and the redundant effort of wrapping these in lambdas over and over again could be spared. Test script: --------------- $f = 'or'; $example_1 = $g($g(TRUE, $g(FALSE, TRUE)), FALSE); $example_2 = array_reduce(array(TRUE, FALSE), $f, FALSE); $example_3 = call_user_func( function($op) { return $op(TRUE, FALSE) }, $f); // Example 4 function or($x, $y) { return $x or $y; } // Example 5 function mult($x, $y) { return $x * $y; } // Example 6 function plus($x, $y = NULL) { return is_null($y)? +$x : $x + $y; } function minus($x, $y = NULL) { return is_null($y)? -$x : $x - $y; } $example_7 = call_user_func('+', 10, 5); Expected result: ---------------- $example_1 == TRUE; $example_2 == TRUE; $example_3 == TRUE; or(TRUE, FALSE) == TRUE; mult(5, 3) == 15; plus(10) == 10; plus(4, 3) == 7; minus(5) == -5; minus(8, 7) == 1; $example_7 == 15; Actual result: -------------- $example_1 -> Undefined function 'or' $example_2 -> Undefined function 'or' $example_3 -> Undefined function 'or' $example_4 -> Unexpected T_LOGICAL_OR $example_7 -> Warning: First argument is expected to be a valid callback ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=66368&edit=1