short-circuiting

Sorry if this sounds like a really silly question. But I Googled the web and also Googled specifically both the php.net site and the stackoverflow.com site. I know PHP does short circuit lazy evaluation when using and, or, &&, || operators, but where is it stated loud and clear in the PHP manual??? I found only Wikipedia as the only 'trusted' source that say PHP does lazy evaluation on these operators. Closest thing I can find to an 'official' mention of PHP's short-circuit implementation: http://php.net/manual/en/language.operators.logical.php This is not an uncommon feature of expression

Which of these subroutines is not like the other? sub or1 { my ($a,$b) = @_; return $a || $b; } sub or2 { my ($a,$b) = @_; $a || $b; } sub or3 { my ($a,$b) = @_; return $a or $b; } sub or4 { my ($a,$b) = @_; $a or $b; } I came to Perl 5 from C and Perl 4 and always used || until I saw more scripts using or and I liked the way it looked. But as the above quiz shows, it's not without its pitfalls for the unwary. For people who use both constructs or who use a lot of or , what rules of thumb do you use to decide which construct to use and make sure the code is doing what you think it is doing?

Prompted by the discussion here The docs suggest some equivalent code for the behaviour of all and any Should the behaviour of the equivalent code be considered part of the definition, or can an implementation implement them in a non-shortcircuit manner? Here is the relevant excerpt from cpython/Lib/test/test_builtin.py def test_all(self): self.assertEqual(all([2, 4, 6]), True) self.assertEqual(all([2, None, 6]), False) self.assertRaises(RuntimeError, all, [2, TestFailingBool(), 6]) self.assertRaises(RuntimeError, all, TestFailingIter()) self.assertRaises(TypeError, all, 10) # Non-iterable

I want to consult SQL Server OR short-circuit Code: DECLARE @tempTable table ( id int ) INSERT @tempTable(id) values(1) DECLARE @id varchar(10) SET @id = 'x' SELECT * FROM @tempTable WHERE 1=1 OR id = @id --successfully SELECT * FROM @tempTable WHERE @id = 'x' OR id = @id --Exception not Convert 'x' to int Why? 1=1 and @id='x' is true. SQL Server OR operator : whether the short-circuit function？ THANKS Within SQL, there is no requirement that an OR clause breaks early. In other words, it is up to the optimizer whether to check both conditions simutaneously. I am not an expert in the MSSQL

I saw this line in the jQuery.form.js source code: g && $.event.trigger("ajaxComplete", [xhr, s]); My first thought was wtf?? My next thought was, I can't decide if that's ugly or elegant. I'm not a Javascript guru by any means so my question is 2-fold. First I want to confirm I understand it properly. Is the above line equivalent to: if (g) { $.event.trigger("ajaxComplete", [xhr, s]); } And secondly is this common / accepted practice in Javascript? On the one hand it's succinct, but on the other it can be a bit cryptic if you haven't seen it before. deceze Yes, your two examples are

What is the difference between the & and && logical operators in MATLAB? The single ampersand & is the logical AND operator. The double ampersand && is again a logical AND operator that employs short-circuiting behaviour. Short-circuiting just means the second operand (right hand side) is evaluated only when the result is not fully determined by the first operand (left hand side) A & B (A and B are evaluated) A && B (B is only evaluated if A is true) Loren && and || take scalar inputs and short-circuit always. | and & take array inputs and short-circuit only in if/while statements. For