short-circuiting

问题 I thought C shell script will behave like C and use short circuit evaluation for logical operators. if ((! -e $cache ) || ("`find $monitor -newer $cache`" != "")) then ... endif But in the if statement, even if the first condition is true, the second is checked giving me errors. Do we have a short circuit logical OR in C shell script? 回答1: Usually, && and || are short-circut. Consider something like this: $ false && echo foo $ true || echo foo In both cases, foo won't be put out. But, AFAIK

问题 I am reading about Java streams' short-circuiting operations and found in some articles that skip() is a short-circuiting operation. In another article they didn't mention skip() as a short-circuiting operation. Now I am confused; is skip() a short-circuiting operation or not? 回答1: From the java doc under the "Stream operations and pipelines" section : An intermediate operation is short-circuiting if, when presented with infinite input, it may produce a finite stream as a result . A terminal

问题 This question already has answers here : What a strange syntax? (3 answers) Closed 5 years ago . What does this line parent && (this.parent.next = this); mean? It just looks like its sitting there, doing nothing, not an if statement or a promise or anything. Is there a name for this style of coding? var Particle = function(i, parent) { this.next = null; this.parent = parent; parent && (this.parent.next = this); this.img = new Image(); this.img.src = "http://www.dhteumeuleu.com/images/cloud_01

问题 My understanding of short circuit evaluation is that an expression is only called when needed in an if statement. Does Go follow this? For instance, would I get better performance on average from: if !isValidQueryParams(&queries) || r == nil || len(queries) == 0 { return "", fmt.Errorf("invalid querystring") } ...to this: if r == nil || len(queries) == 0 || !isValidQueryParams(&queries) { return "", fmt.Errorf("invalid querystring") } ...since isValidQueryParams is a function with much more

问题 Logical operators in Python are lazy. With the following definition: def func(s): print(s) return True calling the or operator >>> func('s') or func('t') 's' only evaluates the first function call, because or recognizes that the expression evaluates to True , irregardless of the return value of the second function call. and does behave analogously. However, when using any() (analogously: all() ) in the following way: >>> any([func('s'), func('t')]) 's' 't' all function calls are evaluated,

问题 From this question, a neat answer about using COALESCE to simplify complex logic trees. I considered the problem of short circuiting. For instance, in functions in most languages, arguments are fully evaluated and are then passed into the function. In C: int f(float x, float y) { return x; } f(a, a / b) ; // This will result in an error if b == 0 That does not appear to be a limitation of the COALESCE "function" in SQL Server: CREATE TABLE Fractions ( Numerator float ,Denominator float )

问题 From this question, a neat answer about using COALESCE to simplify complex logic trees. I considered the problem of short circuiting. For instance, in functions in most languages, arguments are fully evaluated and are then passed into the function. In C: int f(float x, float y) { return x; } f(a, a / b) ; // This will result in an error if b == 0 That does not appear to be a limitation of the COALESCE "function" in SQL Server: CREATE TABLE Fractions ( Numerator float ,Denominator float )

问题 I'm seeing some behavior that doesn't make sense to me when I run a bash script with the -e option that has multiple commands strung together with && s and one of them fails. I would expect the script to stop on the failed command and return the exit status, but instead it just executes the rest of the script happily. Here are examples that make sense to me: $ false && true; echo $? 1 $ bash -xe -c "false && true"; echo $? + false 1 $ bash -xe -c "false; true"; echo $? + false 1 And here is

问题 Recently, I've come across a piece of code like this (not the real one, but a shorter example based upon it): #include <stdio.h> int main() { int n; printf ("n? "); scanf ("%d", &n); n%2 && printf ("N is odd\n"); /* <-- this is it */ return 0; } In case anybody didn't get it, this code is the equivalent of: int main() { int n; printf ("n? "); scanf ("%d", &n); if (n%2) printf ("N is odd\n"); return 0; } A disassembly of this code compiled with GCC 4.4.5-8 for x86-64 bits gives this for the

问题 I have the following simple short-circuit statement that should show either a component or nothing: {profileTypesLoading && <GeneralLoader />} If the statement is false, it renders a 0 instead of nothing. I have done a console.log(profileTypesLoading) just to see quickly what the status of the profileTypesLoading property is and it's either 1 or 0 as expected. 0 should be false... causing nothing to render. Right? Any idea why this would happen? 回答1: Since your condition is falsy and so doesn