short-circuiting | 易学教程

Short circuit evaluation using procedures

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问题 I am currently developing a compiler for a very limited object oriented language. I want to treat all values as objects and operators on those values will be implemented as methods. The compiler transforms the program into assembler for a stack-based virtual machine. During compilation I transform integer literals into objects of a special "Integer" class. Arithmetic operators are implemented as methods of that class (using inline assembler). So that 4 + 5 basically equals to 4.add(5) . The

Is there a Python idiom for evaluating a list of functions/expressions with short-circuiting?

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I wrote a simple script to solve a "logic puzzle", the type of puzzle from school where you are given a number of rules and then must be able to find the solution for problems like "There are five musicians named A, B, C, D, and E playing in a concert, each plays one after the other... if A goes before B, and D is not last ... what is the order of who plays when?" etc. To evaluate possible solutions, I wrote each "rule" as a separate function which would evaluate if a possible solution (represented simply as a list of strings) is valid, for example #Fifth slot must be B or D def rule1(solution

Are fold expressions subject to short-circuiting?

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问题 In C++17, are fold expressions subject to short-circuiting when used with && or || as their operator? If so, where is this specified? 回答1: Yes, fold expressions using && or || as the operator can short-circuit, subject to the usual caveat that it happens for the built-in meaning, but not for an overloaded operator function. The meaning of a fold-expression is defined in [temp.variadic]/9: The instantiation of a fold-expression produces: ((E_1 op E_2) op ... ) op E_N for a unary left fold, E_1

Does short circuiting make execution of the program faster, and is analysing which statement to put first in the condition statement worth it? [closed]

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Closed . This question is opinion-based. It is not currently accepting answers. Learn more . Want to improve this question? Update the question so it can be answered with facts and citations by editing this post . Closed 3 years ago . For instance (Lets say we are talking about C++ if that makes a differnce), In an && operator if I know that one statement will result to 0 more often/has a higher chance then the other statement should I put that on the left side, and the other statement on the right? Same goes for || operator if I know that one statement will result to 1 more often/has a higher

Java logical operator (&&, ||) short-circuit mechanism

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As I was reading a colleague's Java code, I stumbled upon an army of if/else statements. In these statements, several && and || operators were fighting each other without any help from parenthesis. I simplified the statements into: if (true || true && false) return true; else return false; What do you think the result would be? Honestly, I thought it would be false , but it seems short-circuiting doesn't work like I expected. In this case, the result is true . The short-circuit mechanism seems to consider the whole expression as true when it finds true immediately followed by || . But in the

Short-circuit evaluation like Python's “and” while storing results of checks

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问题 I have multiple expensive functions that return results. I want to return a tuple of the results of all the checks if all the checks succeed. However, if one check fails I don't want to call the later checks, like the short-circuiting behavior of and . I could nest if statements, but that will get out of hand if there are a lot of checks. How can I get the short-circuit behavior of and while also storing the results for later use? def check_a(): # do something and return the result, # for

Any difference between Lazy evaluation and Short-circuit evaluation?

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问题 From Wikipedia: Lazy evaluation is: In programming language theory, lazy evaluation or call-by-need is an evaluation strategy which delays the evaluation of an expression until its value is needed Short-circuit evaluation is: Short-circuit evaluation, minimal evaluation, or McCarthy evaluation denotes the semantics of some Boolean operators in some programming languages in which the second argument is only executed or evaluated if the first argument does not suffice to determine the value of

Java 8 stream short-circuit

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问题 Reading up a bit on Java 8, I got to this blog post explaining a bit about streams and reduction of them, and when it would be possible to short-circuit the reduction. At the bottom it states: Note in the case of findFirst or findAny we only need the first value which matches the predicate (although findAny is not guaranteed to return the first). However if the stream has no ordering then we’d expect findFirst to behave like findAny . The operations allMatch , noneMatch and anyMatch may not

Calling methods inside if() - C#

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I have a couple of methods that return a bool depending on their success, is there anything wrong with calling those methods inside of the IF() ? //&& makes sure that Method2() will only get called if Method1() returned true, use & to call both methods if(Method1() && Method2()) { // do stuff if both methods returned TRUE } Method2() doesn't need to fire if Method1() returns FALSE. Let me know there's any problem with the code above. thank you. EDIT: since there was nothing wrong with the code, I'll accept the most informative answer ... added the comment to solve the "newbie & &&" issue I'll

How to avoid short-circuit evaluation on

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I'm working with Ruby on Rails and would like to validate two different models : if (model1.valid? && model2.valid?) ... end However, "&&" operator uses short-circuit evaluation (i.e. it evaluates "model2.valid?" only if "model1.valid?" is true), which prevents model2.valids to be executed if model1 is not valid. Is there an equivalent of "&&" which would not use short-circuit evaluation? I need the two expressions to be evaluated. Try this: ([model1, model2].map(&:valid?)).all? It'll return true if both are valid, and create the errors on both instances. & works just fine. irb(main):007:0>