Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar if
fooptr is NULL? Can I make sure it is evaluated from left to right or should
I have nested if-statements instead?
Thanks for any replies
/ William Payne
6  1608 
William Payne wrote:
Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar if
fooptr is NULL? Can I make sure it is evaluated from left to right or should
I have nested if-statements instead?
In x && y, it is guaranteed that y is not evaluated if x is already false.
Same for x || y : if x is already true, y is not evaluated at all.
Which books are you using, that do not mention 'shortcut evaluation' ?
--
Karl Heinz Buchegger kb******@gascad.at
William Payne wrote:
Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar if
fooptr is NULL? Can I make sure it is evaluated from left to right or should
I have nested if-statements instead?
In x && y, it is guaranteed that y is not evaluated if x is already false.
Same for x || y : if x is already true, y is not evaluated at all.
Which books are you using, that do not mention 'shortcut evaluation' ?
--
Karl Heinz Buchegger kb******@gascad.at
William Payne wrote:
Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar if
fooptr is NULL? Can I make sure it is evaluated from left to right or should
I have nested if-statements instead?
You're golden -- yes, the statement is safe.
The behavior is called 'short circuit', and evaluated left to right.
William Payne wrote:
Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar if
fooptr is NULL? Can I make sure it is evaluated from left to right or should
I have nested if-statements instead?
You're golden -- yes, the statement is safe.
The behavior is called 'short circuit', and evaluated left to right.
"Karl Heinz Buchegger" <kb******@gascad.at> wrote in message
news:40***************@gascad.at... William Payne wrote:
Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar
if fooptr is NULL? Can I make sure it is evaluated from left to right or
should I have nested if-statements instead?
In x && y, it is guaranteed that y is not evaluated if x is already false.
Same for x || y : if x is already true, y is not evaluated at all.
Which books are you using, that do not mention 'shortcut evaluation' ?
--
Karl Heinz Buchegger
kb******@gascad.at
Thanks for the quick reply, Karl. No need for a nested if-statement then,
just as I thought. And to answer your question: I don't have access to a C++
text except Josuttis Standard Library Book at the moment. =/
/ William Payne
"Karl Heinz Buchegger" <kb******@gascad.at> wrote in message
news:40***************@gascad.at... William Payne wrote:
Consider the following code:
struct foo
{
char* bar;
};
// fooptr is of type foo*
if(fooptr != NULL && fooptr->bar != NULL)
{
cout << fooptr->bar << endl;
}
Is the if-statement safe, meaning it won't try to evaluate fooptr->bar
if fooptr is NULL? Can I make sure it is evaluated from left to right or
should I have nested if-statements instead?
In x && y, it is guaranteed that y is not evaluated if x is already false.
Same for x || y : if x is already true, y is not evaluated at all.
Which books are you using, that do not mention 'shortcut evaluation' ?
--
Karl Heinz Buchegger
kb******@gascad.at
Thanks for the quick reply, Karl. No need for a nested if-statement then,
just as I thought. And to answer your question: I don't have access to a C++
text except Josuttis Standard Library Book at the moment. =/
/ William Payne This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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