How does C++ handle &&? (Short-circuit evaluation) [duplicate]
When encountering a (bool1 && bool2), does c++ ever attempts to check bool2 if bool1 was found false or does it ignore it the way PHP does?
Sorry if it is too basic of a question, but I really could not find a mentioning of that neither in Schildt nor on the Internet.
Yes, the &&
operator in C++ uses short-circuit evaluation so that if bool1
evaluates to false
it doesn't bother evaluating bool2
.
"Short-circuit evaluation" is the fancy term that you want to Google and look for in indexes.
The same happens with the ||
operator, if bool1
evaluates to true
then the whole expression will evaluate to true, without evaluating bool2
.
In case you want to evaluate all expressions anyway you can use the &
and |
operators.
C++ does use short-circuit logic, so if bool1
is false, it won't need to check bool2
.
This is useful if bool2 is actually a function that returns bool, or to use a pointer:
if ( pointer && pointer->someMethod() )
without short-circuit logic, it would crash on dereferencing a NULL pointer, but with short-circuit logic, it works fine.
That is correct (short-cicuit behavior). But beware: short-circuiting stops if the operator invoked is not the built-in operator, but a user-defined operator&&
(same with operator||
).
Reference in this SO
The &&
operator short circuits in C++ - if bool1
was false in your example, bool2
wouldn't be checked/executed.