Well if the variable you are applying !! is not already a bool(either zero or one) then it will normalize the value to either 0 or 1. With respect to __builtin_expect this kernel newbies thread discusses the notation and one of the responses explains (emphasis mine): The signature of __builtin_expect http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html) is: long __builtin_expect (long … Read more
yes, it’s two nots. !!a is 1 if a is non-zero and 0 if a is 0 You can think of !! as clamping, as it were, to {0,1}. I personally find the usage a bad attempt to appear fancy.
The & operator performs logical “and” operation for bool operands and is not short circuited. It’s not a sequence point. You cannot rely on the order of evaluation of the operands. However, it’s guaranteed that both operands are evaluated. I do not recommend doing this. Using temporary variables is a better solution. Don’t sacrifice readability … Read more
>>> [i for i,v in enumerate(a) if v > 4] [4, 5, 6, 7, 8] enumerate returns the index and value of each item in an array. So if the value v is greater than 4, include the index i in the new array. Or you can just modify your list in place and exclude … Read more
This will match any character that is a word and is not a p: ((?=[^p])\w) To solve your example, use a negative look-ahead for “My” anywhere in the input, ie (?!.*My): ^(?!.*My)((?<=(so|me|^))big(com?pl{1,3}ex([pA]t{2}ern) Note the anchor to start of input ^ which is required to make it work.
It is not as simple as double negation. For example, if you have x == 5, and then apply two ! operators (!!x), it will become 1 – so, it is used for normalizing boolean values in {0, 1} range. Note that you can use zero as boolean false, and non-zero for boolean true, but … Read more
The and and or operators do return one of their operands, not a pure boolean value like True or False: >>> 0 or 42 42 >>> 0 and 42 0 Whereas not always returns a pure boolean value: >>> not 0 True >>> not 42 False
Updated answer: Apologies, I missed the word “logical” in your question even though it is there. (I’ve taken the liberty of emphasizing it a bit with an edit.) Consider the case where you want any side-effects to always occur, regardless of whether the left-hand expression evaluates true or false. E.g., contrast: if (foo() & bar()) … Read more
Try adding some parentheses to group things logically: IF (DL-CLASS-STANDING = ‘First Yr’ OR ‘Second Yr’) AND (GRAD-STAT-IN = ‘ ‘ OR ‘X’)