Program that counts # of letters

[bookmark]

Hi I'm trying to make a program that returns the number of letters in a string but it seems that the function I have is not working as it returns 0 every time. Can someone check what I'm doing wrong? Thanks in advanced.

#include<iostream>
#include<string>
using namespace std;

unsigned letters(const string a);

int main(){
	int i;
	string a;
	cin >> a;
	cout << letters(a);
	system("pause");
}


unsigned letters(const string a){
	int i;
	int countL = 0;
	for(i=0;a[i]!='\0';i++){		
		if (a[i] >= 'A' && a[i] <='Z' && a[i] >= 'a' && a[i] <= 'z')
			countL++;
}
	return countL;
}

[jonsca]

std::string s don't (EDIT: necessarily) end in '\0' so you have to check and see if you've exceeded the length (which is accessed by the string object's .length() method)

[seanbp]

Should the function definition have a type?

[jonsca]

Should the function definition have a type?

unsigned is a type, unless I'm misunderstanding your question...

[seanbp]

The int is implied. Don't remember reading that. If there's no null terminator wouldn't the code run an infinite loop? bookmark says it returns.

[bookmark]

yeah it returns a 0

[seanbp]

for (i = 0; i < a.length(); i++) 
if ((a[i] >= 'A' && a[i] <= 'Z') || (a[i] >= 'a' && a[i] <= 'z'))

:)

[jonsca]

It gave me pause, but I found this thread http://bytes.com/topic/c/answers/877992-does-object-c-std-string-type-terminates-null-character which would seem to indicate that it just happens to work out that way in some implementations, so I wouldn't count on it working. Use the length member.

[jonsca]

for (i = 0; i < a.length(); i++) 
if ((a[i] >= 'A' && a[i] <= 'Z') || (a[i] >= 'a' && a[i] <= 'z'))

:)

Good catch, I hadn't gotten that far yet, though you should at least give him/her the means to figure out why the logic was wrong.

[bookmark]

The code that seanbp made it work. thanks seanbp.