string letter detection?

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February 25th, 2003, 03:23 PM

andy3109

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string letter detection?

Is there a way that I can tell if a string has a certain letter in it? For example:

string asdfa;
cout<<"type in string";
cin>>asdfa;

if...(there is the letter 'a' in string)
{
cout << "Your string contained the letter 'a' which isn't allowed in my program";
}

else if (if there isn't letter 'a' in string)
{
continue...
}

So I guess I am askign if there is a way I can detect a letter in a string and react based on if the user has typed that letter or not. Thanks!

-andy

__________________
hmmm...

February 25th, 2003, 03:32 PM

Scorpions4ever

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Use strchr() or strstr()

February 25th, 2003, 03:55 PM

andy3109

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hmm not formiliar with those..ill do some research. Thanks!

-andy

February 25th, 2003, 04:48 PM

7stud

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andy3109,

Those functions are going to implement a process whereby you examine each character in the string using array notation. Using the string length as the loop control, you can examine each character of the string like this:

Code:

string text;
char looking_for = 'a';
bool found_flag = false;

for(int i=0; i<text.length(); i++)
{
	if(text[i]==looking_for)
	{
		found_flag=true;
		break;
	}
}

February 25th, 2003, 06:29 PM

vpopper

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Use the STL:

Code:

#include <algorithm>

std::string::size_type pos =0;

pos = asdfa.find_first_of("x", 0);  // find "x"

if (pos == std::string::npos)
    // nope
else
    // found

February 25th, 2003, 07:29 PM

andy3109

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hmm..both interesting ways..I understand 7stud more, but thanks for your reply vpopper!

-andy

February 25th, 2003, 07:43 PM

andy3109

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what if you wanted to text a rage of letters, as A through F.

February 25th, 2003, 08:48 PM

7stud

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All characters are stored as integer codes. You can look up the ASCII codes for all the characters--there's a table of codes in the appendix of my book, so check yours for the table.

ASCII codes for A-F are 65-70, so you can test whether text[i] is between 65 and 70.

Last edited by 7stud : February 25th, 2003 at 08:52 PM.

February 25th, 2003, 09:37 PM

andy3109

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got it to work..thanks man.

string letter detection?

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