String contains function

Hi all:

In Java strings, there is a String.contains method that will tell you whether a particular string contains another string as its substring. Is there something that is the same in C++? I'm trying to use string.find(string input), but that seems to return -1 every time.

Thanks.

Edit: This has progressed to a unicode/ascii problem. Anyone can shed some light regarding Unicode processing/detection?

Thanks again.

Yes, the find member function of std::string should work, assuming you are working with such strings. If the substring is not found, std::string::npos would be returned.

If you are using null terminated strings, then strstr() from C++'s C legacy should be used.

Quote:

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Originally Posted by laserlight

Yes, the find member function of std::string should work, assuming you are working with such strings. If the substring is not found, std::string::npos would be returned.

If you are using null terminated strings, then strstr() from C++'s C legacy should be used.

---

Thanks. However, that doesn't seem to be working. BTW, what does null terminated strings mean? I presume the getline function does give a null terminated string (I could be very wrong)?

Here's what I'm working with:

Code:

---

string currentLine;
        int line = 0;
        ifstream input (file);
        //input.open(file, ios::in);
        while(!input.eof())
        {
                getline(input, currentLine);
                line ++;
                if (currentLine.find(contains) != string::npos)
                {
                        int a = currentLine.find(contains);
                        cout <<"[" <<line <<"] " <<a <<"\n\n";
                }
        }

---

Quote:

---

BTW, what does null terminated strings mean? I presume the getline function does give a null terminated string (I could be very wrong)?

---

By null terminated string I mean the C-style strings that use '\0' to denote one past the last character of the string. As for getline, that depends on which getline you refer to. In this case, std::getline works with std::string.

I have no clue as to what data you are working with, so it could well be a problem with your data rather than with your code. To convince yourself that find works, try:

Code:

---

#include <string>
#include <iostream>

int main() {
        if (std::string("hello world!").find("world") != std::string::npos) {
                std::cout << "found" << std::endl;
        } else {
                std::cout << "not found" << std::endl;
        }
}

---

By the way, you probably shouldnt be testing input.eof() in your loop condition. Rather, test with getline directly.

Code:

---

string currentLine;
int line = 0;
ifstream input(file);
while (getline(input, currentLine))
{
        ++line;
        std::size_type pos = currentLine.find(contains);
        if (pos != string::npos)
        {
                cout << "[" << line << "] " << pos << "\n\n";
        }
}

---

Quote:

---

Originally Posted by laserlight

By null terminated string I mean the C-style strings that use '\0' to denote one past the last character of the string. As for getline, that depends on which getline you refer to. In this case, std::getline works with std::string.

I have no clue as to what data you are working with, so it could well be a problem with your data rather than with your code. To convince yourself that find works, try:

Code:

---

#include <string>
#include <iostream>

int main() {
        if (std::string("hello world!").find("world") != std::string::npos) {
                std::cout << "found" << std::endl;
        } else {
                std::cout << "not found" << std::endl;
        }
}

---

By the way, you probably shouldnt be testing input.eof() in your loop condition. Rather, test with getline directly.

Code:

---

string currentLine;
int line = 0;
ifstream input(file);
while (getline(input, currentLine))
{
        ++line;
        std::size_type pos = currentLine.find(contains);
        if (pos != string::npos)
        {
                cout << "[" << line << "] " << pos << "\n\n";
        }
}

---

---

Thanks. I can't seem to get the part with the find working...I changed it to look pretty much just like yours :(.

You have a PM btw :).

So I know that "hello world" works, but "HELLO WORLD" doesn't work when I look for "HELLO" - also, if I use something like <html>, it would not find anything. I'm starting to think that this is perhaps a character set conversion problem?

Can anyone shed light on this?

Thanks.

So we've determined that this is a problem between Unicode and ASCII text. Is there an easy way to convert?