All design processes result in compromises between mutually incompatible goals. Unfortunately, the design process for the overloaded && operator in C++ produced a confusing end result: that the very feature you want from && — its short-circuiting behavior — is omitted. The details of how that design process ended up in this unfortunate place, those … Read more
You can simply use != instead.
Yes, short-circuiting and evaluation order are required for operators || and && in both C and C++ standards. C++ standard says (there should be an equivalent clause in the C standard): 1.9.18 In the evaluation of the following expressions a && b a || b a ? b : c a , b using the … Read more
And has precedence over Or, so, even if a <=> a1 Or a2 Where a And b is not the same as Where a1 Or a2 And b, because that would be Executed as Where a1 Or (a2 And b) and what you want, to make them the same, is the following (using parentheses to … Read more
JavaScript traces its ancestry back to C, and C does not have a logical XOR operator. Mainly because it’s not useful. Bitwise XOR is extremely useful, but in all my years of programming I have never needed a logical XOR. If you have two boolean variables you can mimic XOR with: if (a != b) … Read more
Yes, as the other answers pointed out, the set of operators comprising of || and ! is functionally complete. Here’s a constructive proof of that, showing how to use them to express all sixteen possible logical connectives between the boolean variables A and B: True: A || !A A NAND B: !A || !B B … Read more
You can do and with nested conditions: if %age% geq 2 ( if %age% leq 12 ( set class=child ) ) or: if %age% geq 2 if %age% leq 12 set class=child You can do or with a separate variable: set res=F if %hour% leq 6 set res=T if %hour% geq 22 set res=T if … Read more
The shorter ones are vectorized, meaning they can return a vector, like this: ((-2:2) >= 0) & ((-2:2) <= 0) # [1] FALSE FALSE TRUE FALSE FALSE The longer form evaluates left to right examining only the first element of each vector, so the above gives ((-2:2) >= 0) && ((-2:2) <= 0) # [1] … Read more
What you’ve written actually almost works (it would work if all the variables were numbers), but it’s not an idiomatic way at all. (…) parentheses indicate a subshell. What’s inside them isn’t an expression like in many other languages. It’s a list of commands (just like outside parentheses). These commands are executed in a separate … Read more
The != operator serves this purpose for bool values.