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Questions tagged [logical-operators]

Logical operators are symbols that aid in evaluating boolean expressions. These are found in just about every programming language that supports boolean. Common examples are && (AND), || (OR), ! (NOT), == ([value] equal to), === ([value and type] equal to), >= (Greater than or equal to), <= (Less than or equal to), > (Greater than), and < (less than)

Operations:

  • AND: both expressions are TRUE
  • OR: either expression is TRUE
  • NOT: TRUE if the expression is FALSE
  • NAND: the inverse of an AND operation
  • NOR: the inverse of an OR operation
  • XOR: either expression is TRUE but not both
  • XNOR: both must be TRUE or both must be FALSE

In scientific software for statistical computing and graphics, consult ?base::Logic for logical operators.

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How do you get the logical xor of two variables in Python?

How do you get the logical xor of two variables in Python? For example, I have two variables that I expect to be strings. I want to test that only one of them contains a True value (is not None or an empty string): str1 = raw_input("Enter string…
Zach Hirsch
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Logical XOR operator in C++?

Is there such a thing? It is the first time I encountered a practical need for it, but I don't see one listed in Stroustrup. I intend to write: // Detect when exactly one of A,B is equal to five. return (A==5) ^^ (B==5); But there is no ^^…
RAC
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Simple logical operators in Bash

I have a couple of variables and I want to check the following condition (written out in words, then my failed attempt at bash scripting): if varA EQUALS 1 AND ( varB EQUALS "t1" OR varB EQUALS "t2" ) then do something done. And in my failed…
Amit
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Difference between Boolean operators && and & and between || and | in R

According to the R language definition, the difference between & and && (correspondingly | and ||) is that the former is vectorized while the latter is not. According to the help text, I read the difference akin to the difference between an "And"…
Suraj
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Logical operators ("and", "or") in DOS batch

How would you implement logical operators in DOS Batch files?
JoelFan
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Are || and ! operators sufficient to make every possible logical expression?

The logical expression ( a && b ) (both a and b have boolean values) can be written like !(!a || !b), for example. Doesn't this mean that && is "unneccesary"? Does this mean that all logical expressions can be made only using || and !?
JakeTheSnake
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Why is there no logical XOR?

Why is there no logical XOR in JavaScript?
DarkLightA
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SQL Logic Operator Precedence: And and Or

Are the two statements below equivalent? SELECT [...] FROM [...] WHERE some_col in (1,2,3,4,5) AND some_other_expr and SELECT [...] FROM [...] WHERE some_col in (1,2,3) or some_col in (4,5) AND some_other_expr Is there some sort of truth table I…
nc.
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Is short-circuiting logical operators mandated? And evaluation order?

Does the ANSI standard mandate the logical operators to be short-circuited, in either C or C++? I'm confused for I recall the K&R book saying your code shouldn't depend on these operations being short circuited, for they may not. Could someone…
Joe Pineda
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Is it good practice to use the xor operator for boolean checks?

I personally like the exclusive or, ^, operator when it makes sense in the context of boolean checks because of its conciseness. I much prefer to write if (boolean1 ^ boolean2) { //do it } than if((boolean1 && !boolean2) || (boolean2 &&…
Peter
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How do "and" and "or" act with non-boolean values?

I'm trying to learn python and came across some code that is nice and short but doesn't totally make sense the context was: def fn(*args): return len(args) and max(args)-min(args) I get what it's doing, but why does python do this - ie return…
Marcin
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Is there actually a reason why overloaded && and || don't short circuit?

The short circuiting behaviour of the operators && and || is an amazing tool for programmers. But why do they lose this behaviour when overloaded? I understand that operators are merely syntactic sugar for functions but the operators for bool have…
iFreilicht
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Java logical operator short-circuiting

Which set is short-circuiting, and what exactly does it mean that the complex conditional expression is short-circuiting? public static void main(String[] args) { int x, y, z; x = 10; y = 20; z = 30; // T T // T F // F T // F F …
Aaron
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What's the difference between & and && in JavaScript?

What's the difference between & and && in JavaScript? Example code: var first = 123; var second = false; var third = 456; var fourth = "abc"; var fifth = true; alert(first & second); // 0 alert(first & third); // 72 alert(first & fourth); //…
Martin Thoma
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Differences in boolean operators: & vs && and | vs ||

I know the rules for && and || but what are & and |? Please explain these to me with an example.
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