Evaluation order in if statement

[Bogdan]

Hi

I would like to know if the standard specifies the evaluation order
of several conditions, like in the following example:

if (is.eof() || (c == '\n'))

Does is.eof() is evaluated first or is the other way around ?

thanks
Bogdan

 

[Dombo]

Op 24-Nov-11 22:22, Bogdan schreef:

Hi

I would like to know if the standard specifies the evaluation order
of several conditions, like in the following example:

if (is.eof() || (c == '\n'))

Does is.eof() is evaluated first or is the other way around ?

(is.eof()) is evaluated first, and (c == '\n') will not be evaluated at
all if (is.eof())==true.

 

[Paul N]

Op 24-Nov-11 22:22, Bogdan schreef:





(is.eof()) is evaluated first, and (c == '\n') will not be evaluated at
all if (is.eof())==true.

Just to clarify, the operators "||", "&&" and "," are special in this
respect - they guarantee that the first operand is evaluated first,
and that the second is (for || and &&) only evaluated if required. For
other operators such as "+", the operands could be evaluated in either
order.

 

[red floyd]

Just to clarify, the operators "||", "&&" and "," are special in this
respect - they guarantee that the first operand is evaluated first,
and that the second is (for || and&&) only evaluated if required. For
other operators such as "+", the operands could be evaluated in either
order.

Unless the operator has been overridden for a UDT, in which case it's
equivalent to calling:

operator&&(left, right)

In which case evaluation order is undefined. In the OP's case, it's
bool, so it is in fact, left to right.

 

[Rainer Grimm]

Hi,
that's a special form of lazy evaluation, called short-circuit evaluation. Have a look here http://en.wikipedia.org/wiki/Short-circuit_evaluation.

Greetings from Rottenburg,
Rainer