I was expecting the following comparison to give an error: var A = B = 0; if(A == B == 0) console.log(true); else console.log(false); but strangely it returns false. Even more strangely, co...

I understand that an empty string is falsy in javascript and a not-empty string is truthy in javascript. However, why is 'false' truthy in javascript, is there anything explicit in the specificati...

While it is always possible to use mixins or method overrides to modify the Bool coercions, by default what values are considered to be truthy and what values are considered to be falsy? Note: this...

This question is spurred from the answers and discussions of this question. The following snippet shows the crux of the question: >>> bool(NotImplemented) True The questions I have are ...

The empirical behaviour of my Perl 5.26.2 x64 (Cygwin) is that a dualvar is truthy if and only if its string part is truthy: # Falsy number, truthy string => truthy $ perl -MScalar::Util=dualva...

I am interested in the truth value of Python sets like {'a', 'b'}, or the empty set set() (which is not the same as the empty dictionary {}). In particular, I would like to know whether bool(my_set...

I am learning python, but I'm a bit confused by the following result. In [41]: 1 == True Out[41]: True In [42]: if(1): ...: print('111') ...: 111 In [43]: ... == True Out[43]: False <=====...

I have seen the following cases: >>> def func(a): ... if a: ... print("True") ... >>> a = [1, 2, 3] >>> func(a) True >>> a == True False Why does this d...

The documentation clearly states that When this method (__bool__) is not defined, __len__() is called, if it is defined, and the object is considered true if its result is nonzero. If a cl...

import numpy as np a = np.array([0]) b = np.array([None]) c = np.array(['']) d = np.array([' ']) Why should we have this inconsistency: >>> bool(a) False >>> bool(b) False >...

In Groovy it is possible to test collections for null and empty simply by placing the variable by itself inside if like: def collection = [ 'test' ] if(!collection) { //Collection is either null ...

Consider this code: test_string = 'not empty' if test_string: return True else: return False I know I could construct a conditional expression to do it: return True if test_string else False...

In angular.js, there are some code snippets use !! to check whether a value is truthy in if condition. Is it a best practice? I fully understand in return value or other assignment !! is used to m...

One of the limitations of PHP is that objects always evaluate to true. However SplFileinfo (and subclasses such as Symfony's UploadedFile) behave differently: $a = new ArrayIterator(); // or any o...

In IE and Chrome, typing this into the JavaScript console throws an exception: {} == false // "SyntaxError: Unexpected token ==" However, all of these statements are evaluated with no problem: ...

In reading about Perl 6, I see a feature being trumpeted about, where you no longer have to do: return "0 but true"; ...but can instead do: return 0 but True; If that's the case, how does tru...

Let's say I have a something like true && true #=> true Which makes sense, so I try something like: true && "dsfdsf" #=> "dsfdsf" Which surprises me because often times ...

I've been reading about JavaScript hoisting sometime back. JavaScript Scoping and Hoisting by Ben Cherry Two words about “hoisting” by Dmitry Soshnikov and, some more about JavaScript type-coercio...

Is it normal for methods with a question mark to return something that's truthy (for example, a number) to indicate that something is true, or should true itself be returned? Are there any example...