boolean-expression

问题 Is one more readable than the other? At first, I disliked the false === approach but as I see it more and more often, I'm warming up to it. I'm pretty sure they return identical results. 回答1: I greatly prefer false === $var Namely because sometimes you are only using equality and not looking for identity. In which case you write false == $var But sometimes you aren't at the top of your game, and might write false = $var which will give an immediate error, and let's you fix it right away.

问题 This question already has answers here : Closed 9 years ago . Possible Duplicate: Conditional operator cannot cast implicitly? I have run into a peculiar situation and want to know why I have to do it. I'm using .NET 3.5. This works: short foo; if (isValid) foo = -1; else foo = getFoo(); This does not work: short foo; foo = isValid ? -1 : getFoo(); I have to typecast -1: short foo; foo = isValid ? (short)-1 : getFoo(); What does the ternary expression do differently? It considers the -1 to be

问题 This question already has answers here : Closed 9 years ago . Possible Duplicate: Conditional operator cannot cast implicitly? I have run into a peculiar situation and want to know why I have to do it. I'm using .NET 3.5. This works: short foo; if (isValid) foo = -1; else foo = getFoo(); This does not work: short foo; foo = isValid ? -1 : getFoo(); I have to typecast -1: short foo; foo = isValid ? (short)-1 : getFoo(); What does the ternary expression do differently? It considers the -1 to be

问题 Using python, what is the best way to convert a string of ANDs and ORs into disjunctive normal form (also known as "sum of products")? b AND (c OR (a AND d)) becomes (b AND c) OR (b AND a AND d) I would like to also sort these, lexicographically (a AND b AND d) OR (b AND c) 回答1: Maybe this library can help: pyeda here is a method to turn an expression into DNF: to_dnf() Of course you must turn your string into a valid pyeda expression... 回答2: Here is a sample answering partially the question

问题 This question already has answers here : !! c operator, is a two NOT? (4 answers) Closed 6 years ago . I have encountered the following snippet: pt->aa[!!(ts->flags & MASK)] = -val; What does !! (double exclamation marks / exclamation points/ two not operators) stand for in c? Isn't (!!NULL) == NULL ? 回答1: ! is negation. So !! is negation of negation. What is important is the fact that the result will be an int . !!x if x == 0 is !!0 , that is !1 , that is 0 . !!x if x != 0 is !!(!0) , that

问题 This question already has answers here : Evaluate String as a condition Java (8 answers) Closed 2 years ago . I am learning Java now and don't know how to convert an input string(such as "4>1" ) to get a boolean return. The goal that I want to achieve is that, let Java return boolean (true/false) based on the user input, which is in String ? For example, I tried to get a return value of " true " for input " !(4>=10) ". 回答1: There is no easy answer For starters there are no easy solutions. I

问题 Is there any tool or library in java which simplifies a boolean expression formula and gives result. when inputs are like that, exp = (a || a' ) result = 1 exp = ( a || b ) && ( a' || b ) result = b (after simplification) Expressions can be larger or more complex than above. 回答1: IntelliJ supports "intentions" which allow you to simplify boolean expressions within the editor. Alternatively, PMD can report these kind of errors for you (see the boolean rules) 来源： https://stackoverflow.com

问题 Found this little oddity while playing around. >>> 'Hello' == ('Hello' or 'World') True >>> 'Hello' == ('World' or 'Hello') False >>> 'Hello' == ('Hello' and 'World') False >>> 'Hello' == ('World' and 'Hello') True Is there some trick to this logic that I'm not getting? Why is the order of the strings the determining factor of these queries? Should I not be using parentheses at all? Why does changing to "and" flip the outputs? Thanks a buncharooni. 回答1: In Python, all objects may be

问题 A program that prints its input one word per line. int main() { int c; while ((c=getchar()) != EOF) { if (c== ' ' || c== '\n' ||c == '\t') putchar('\n'); else { putchar(c); } } return 0; } The above program prints the result correctly, one word per line. After changing the condition accordingly, I was expecting the program below to also print one word per line. However I am not getting the correct result. Am I making some silly mistake or is something wrong? int main() { int c; while ((c

问题 I'm facing a strange problem in python. I have a maze, x's stand for walls, g is a goal, s is the starting point and the numbers are portals which bring you from one number to the other (e.g. if you go on one of the 2's it will transport you to the other 2). xxxxxxxxxxxxxxxxxxxx x2 x x xxx x x 1 x xxxxx x x s x x x x x xxxxxxx x xx xxxxx x x x g x x 1 x 2 x xxxxxxxxxxxxxxxxxxxx I'm trying to find all portals and put them into an array. So far this works, the program finds all four portals.