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Join Date: Jul 2006
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Practically a Master Poster
hello there, im new in c++...i just want to know how to compare a string to null like:
im using this one, if(&x==0) ...but it does'nt work...
this is what my mentor told me to do...
help..thanks
string x;
cin >> x;
if(x==NULL){
cout << "null";
}
im using this one, if(&x==0) ...but it does'nt work...
this is what my mentor told me to do...
help..thanks
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Join Date: Apr 2007
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Junior Poster
string class has no overloaded "==" operator. You can do
string temp;
cin >> temp;
if(temp.empty())
cout << "null";
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Join Date: Jul 2006
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Practically a Master Poster
uhmm, what about the;
how would compare to null...
btw, thank you...
char temp[100];
how would compare to null...
btw, thank you...
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Join Date: Jun 2006
Location: India
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Given
char temp[100]; I guess you must be talking of how to determine is a string is empty. How about something like if(strlen(temp) == 0) { }. Last edited by ~s.o.s~ : May 10th, 2007 at 10:08 pm.
I don't accept change. I don't deserve to live.
Happiness corrupts people.
Failing to value the lives of others cheapens your own.
Happiness corrupts people.
Failing to value the lives of others cheapens your own.
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Join Date: Dec 2006
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Join Date: Jul 2006
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its not working, i just press enter but it does not alert me that i placed nothing... T_T
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Join Date: Sep 2004
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>i just want to know how to compare a string to null
You don't. NULL is a null pointer and a string object isn't a pointer. Most likely you want to check for an empty string:
or
And such.
>this is what my mentor told me to do...
Your mentor probably thought you were using C-style strings simulated with pointers. Your sample code isn't though, so that advice is useless.
>string class has no overloaded "==" operator.
Yes, it does. That's one of the selling points of the class.
>i just press enter but it does not alert me that i placed nothing...
Post your full program. We don't like playing 20 questions.
You don't. NULL is a null pointer and a string object isn't a pointer. Most likely you want to check for an empty string:
if ( x == "" )
if ( x.empty() )
>this is what my mentor told me to do...
Your mentor probably thought you were using C-style strings simulated with pointers. Your sample code isn't though, so that advice is useless.
>string class has no overloaded "==" operator.
Yes, it does. That's one of the selling points of the class.
>i just press enter but it does not alert me that i placed nothing...
Post your full program. We don't like playing 20 questions.
I'm a programmer. My attitude starts with arrogance, holds steady at condescension, and ends with hostility. Get used to it.
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Join Date: Jun 2006
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> i just press enter but it does not alert me that i placed nothing.
Maybe the newline is getting the best of you...
Maybe the newline is getting the best of you...
I don't accept change. I don't deserve to live.
Happiness corrupts people.
Failing to value the lives of others cheapens your own.
Happiness corrupts people.
Failing to value the lives of others cheapens your own.
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Join Date: Apr 2007
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Junior Poster
In c++ you can compare a "null string" by going (x != npos) Cant you?
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Join Date: Jun 2006
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There is no 'null string' as such, only null pointers. A string instance can't be null because it has just been instantiated. And
x != string::npos doesn't make sense either, one is a string object while the other is most probably an unsigned integer. I don't accept change. I don't deserve to live.
Happiness corrupts people.
Failing to value the lives of others cheapens your own.
Happiness corrupts people.
Failing to value the lives of others cheapens your own.
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