Cannot convert type 'int' to 'bool'

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

John - 22 Sep 2007 05:39 GMT

The following code:

int test = 1;
bool isTrue = (bool)test;

results in a compiler error:

Cannot convert type 'int' to 'bool'

wtf, any ideas on how to work around this?

Reply to this Message

Jonathan Wood - 22 Sep 2007 05:48 GMT

I don't know why you get this error but it could be related with bool values
being limited to 1 or 0. In this case, the int is 1, but I wouldn't want the
compiler trying to determine stuff like that--too much overhead.

How about something like this:

bool isTrue = (test != 0);

Signature

Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com

> The following code:
>
[quoted text clipped - 6 lines]
>
> wtf, any ideas on how to work around this?

Reply to this Message

John - 22 Sep 2007 07:20 GMT

> How about something like this:

> bool isTrue = (test != 0);

Yes, it seems that their is no implicit conversion of int to bool,
therefore the only recourse is to specifically use an equivalence
operator. Oh well, must have something to do with the overhead of the
JIT. Well, not that the JIT implicitly has overhead, it's just that we
have to specifically spoon feed it exactly we want.

Reply to this Message

Jon Skeet [C# MVP] - 22 Sep 2007 08:08 GMT

> > bool isTrue = (test != 0);

> Yes, it seems that their is no implicit conversion of int to bool,
> therefore the only recourse is to specifically use an equivalence
> operator. Oh well, must have something to do with the overhead of the
> JIT. Well, not that the JIT implicitly has overhead, it's just that we
> have to specifically spoon feed it exactly we want.

No, it's got nothing to do with JIT overhead - it's to do with program
correctness. An implicit conversion from int to bool could easily lead
to unintended consequences, such as:

int x;
if (x=3)
{
...
}

Conceptually an integer isn't true or false. Just because C and C++
have traditionally treated any non-zero value as "true" doesn't mean
it's a good idea.

Signature

Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

Reply to this Message

Registered User - 22 Sep 2007 07:25 GMT

>The following code:
>
[quoted text clipped - 6 lines]
>
>wtf, any ideas on how to work around this?

bool isTrue = Convert.ToBoolean(test);

You will find that non-zero integer arguments to Convert.ToBoolean all
return true.

regards
A.G.

Reply to this Message

Göran Andersson - 23 Sep 2007 22:49 GMT

>> The following code:
>>
[quoted text clipped - 14 lines]
> regards
> A.G.

The Convert.ToBoolean(int) method is implemented as:

public static bool ToBoolean(int value) {
return (value != 0);
}

So it's the same as doing the operation yourself:

bool isTrue = (test != 0);

Perhaps the compiler manages to inline the method call, so that the
generated code is the same in both cases. Either way the difference in
performance is normally negligable, so you should just go with the one
that best describes why you are doing the conversion.

Signature

Göran Andersson
_____
http://www.guffa.com

Reply to this Message

Som Nath Shukla - 22 Sep 2007 08:00 GMT

check it its working
int k= 1;
bool b = Convert.ToBoolean(k);

> The following code:
>
[quoted text clipped - 6 lines]
>
> wtf, any ideas on how to work around this?

Reply to this Message

Cannot convert type 'int' to 'bool'

Free Magazines