React showing 0 instead of nothing with short-circuit (&&) conditional component

Since your condition is falsy and so doesn’t return the second argument (<GeneralLoader />), it will return profileTypesLoading, which is a number, so react will render it because React skips rendering for anything that is typeof boolean or undefined and will render anything that is typeof string or number: To make it safe, you can … Read more

Short circuit on |= and &= assignment operators in C#

The C# specification guarantees that both sides are evaluated exactly once from left-to-right and that no short-circuiting occurs. General rules for expressions with embedded expressions The following rules apply to these kinds of expressions: parenthesized expressions (§7.6.3), element access expressions (§7.6.6), base access expressions with indexing (§7.6.8), increment and decrement expressions (§7.6.9, §7.7.5), cast … Read more

What is the difference between Perl’s ( or, and ) and ( ||, && ) short-circuit operators?

Due to the low precedence of the ‘or’ operator, or3 parses as follows: sub or3 { my ($a,$b) = @_; (return $a) or $b; } The usual advice is to only use the ‘or’ operator for control flow: @info = stat($file) or die; For more discussion, see the perl manual:

Is there actually a reason why overloaded && and || don’t short circuit?

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

C++ short-circuiting of booleans

No, the B==2 part is not evaluated. This is called short-circuit evaluation. Edit: As Robert C. Cartaino rightly points out, if the logical operator is overloaded, short-circuit evaluation does not take place (that having been said, why someone would overload a logical operator is beyond me).

Is relying on && short-circuiting safe in .NET?

Yes. In C# && and || are short-circuiting and thus evaluates the right side only if the left side doesn’t already determine the result. The operators & and | on the other hand don’t short-circuit and always evaluate both sides. The spec says: The && and || operators are called the conditional logical operators. They … Read more

Does Python’s `all` function use short circuit evaluation?

Yes, it short-circuits: >>> def test(): … yield True … print(‘one’) … yield False … print(‘two’) … yield True … print(‘three’) … >>> all(test()) one False From the docs: Return True if all elements of the iterable are true (or if the iterable is empty). Equivalent to: def all(iterable): for element in iterable: if not … Read more