adding a bool to a string

Hi All,

I'm trying to print boolean values and after I searched the entire web,
I couldn't find anything that does this =/ The code that I ended up
using is as follows:

string boolString(Object* obj_, size_t maxOutput_){
string string_;

for (size_t i=0; i<maxOutput_; i++){

if( sizeof(obj_->boolean(i)) == sizeof(bool) ){
if (obj_->boolean(i) == true)
string_ += "1";
else
string_ += "0";
}
}

return string_;
}

Is there any way to simplify this code?

aaragon wrote:
What is the above line supposed to do? What does obj_->boolean(i) return?
Note that sizeof is always computed at compile time.
string boolString(Object* obj_, size_t maxOutput_){
stringstream stream_;

for (size_t i=0; i<maxOutput_; i++)
// depending on the return type of boolean(), you can remove the cast
stream_ << bool(obj_->boolean(i));

return stream_.str();
}

aaragon wrote:Why do you need to check the size? What does it give you?
This could be written

string_ += (obj_->boolean(i) ? '1' : '0');

which I find a bit simpler.

Also, consider that you call 'boolean' member twice here (once to
check the size and the other to actually get the value); if the
function has side effects, calling it twice may not be what you
want.
V
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Victor Bazarov wrote:I need to check the size because the function may not return a bool but
an integer for example.

Rolf Magnus wrote:Sometimes boolean() may return an integer, so doing a cast to a boolean
is not a good idea. This is the reason behind the check of the size of
whatever type boolean() returns. I thought that the sream can
automatically convert to 1 or 0 from a boolean as

stream_ += boolean(i);

but this is not the case. However, if I repeat the previous with an
integer, it works fine.

Rolf Magnus wrote:Consider that some locales do not have '1' or '0' as the default
for outputting a bool value. If the OP wanted '1' or '0', it should
probably be explicit.

And how is using a stringstream simpler (better) than, say,

for (size_t i=0; i<maxOutput_; i++)
string_ += (bool(obj_->boolean(i)) ? '1' : '0');

return string_;

?

V
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"aaragon" <alejandro.aragon@gmail.comwrote in message
news:1163617470.334923.67870@k70g2000cwa.googlegro ups.com...And how do you know that a value is a bool just because it's the same size
as one?

Also, boolean() is your own function, so you should already know what its
return type is. It can't sometimes return a bool and other times return an
int. (Unless, I guess, if "boolean" isn't really a function member of obj_
at all, but is instead a function pointer which you assign elsewhere.)

-Howard

aaragon wrote:So? An integer is convertible to bool. Besides, sizes of 'bool' and
'int' _can_ be the same. The check is no good. You need to check
'typeid' to be sure.
V
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>Well, this definitely will work for booleans. But, the object I'm
working on, would also be a container for other values (say double,
integers) in which case boolean representation is no longer useful
(forget about the name boolean(i), it could be anything, like
value(i)). Therefore, the cast that you're using is not useful
anymore.

Howard wrote:If it's a function pointer, the return value type is part of the type
of that pointer. C++ is strict in that regard. You cannot have return
value types change arbitrarily during run-time.

V
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aaragon wrote:If for some twisted reason the 'boolean' function returns an 'int'
and not a 'bool', it shouldn't be used here, which means you need
to employ some kind of templated mechanism for rejecting classes
with 'boolean' members returning anything except 'bool'. See your
favourite C++ book on how to specialise your function on that.

V
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"Victor Bazarov" <v.Abazarov@comAcast.netwrote in message
news:ejfp4p$hhq$1@news.datemas.de...
Oh, right, of course. Thanks.

-Howard

aaragon wrote:
Could you elaborate on how you think you did that? It's not possible. A
function's return type is fixed at compile time. Somewhere, you declared
the function, and part of that declaration is the return type. So if
boolean() returns a bool, it will always do that.
The size of bool depends on the implementation. Most often, it's the same as
char or the same as int.
You need operator <<, not += to put something into a stream.