Simple question of how execution happens in C++ and Python.
If I have an if condition
if ((b == c) and (a == b))
My doubt in the above condition is,
if first part i.e. (b == c) is false
then the second condition i.e. (a == b) is executed or no matter what first part output was, second parts gets executed irrespective of that.
Both in c++ and python, and and or operations support short-circuiting, that is, if the left part of and is false, the right part is not evaluated; if the left part of or is true, the right part is not evaluated.
In c++ this is per standard (§5.14/1):
The && operator groups left-to-right. The operands are both contextually converted to bool (Clause 4 ). The result is true if both operands are true and false otherwise. Unlike & , && guarantees left-to-right evaluation: the second operand is not evaluated if the first operand is false
and (§5.15/1):
The || operator groups left-to-right. The operands are both contextually converted to bool (Clause 4 ). It returns true if either of its operands is true , and false otherwise. Unlike | , || guarantees left-to-right evaluation; moreover, the second operand is not evaluated if the first operand evaluates to true .
In python that is also mentioned in the docs (python2, python3):
x or y | if x is false, then y, else x (1)
x and y | if x is false, then x, else y (2)Notes:
(1) This is a short-circuit operator, so it only evaluates the second argument if the first one is False.
(2) This is a short-circuit operator, so it only evaluates the second argument if the first one is True.
