string methods hard time

This is a discussion on string methods hard time within the C++ Programming forums, part of the General Programming Boards category; Hello people, can anyone explain me why output from this program Code: #include <iostream> #include <string> using namespace std; int ...

  1. #1
    Registered User Micko's Avatar
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    string methods hard time

    Hello people,
    can anyone explain me why output from this program
    Code:
    #include <iostream>
    #include <string>
    
    using namespace std;
    
    int main()
    {
    	string str = "This is, you shouldn't see this, just a test!";
    	string :: size_type start, end;
    	string delim = ",";
    
    	start = str.find(delim);
    	if (start == string::npos)
    	{
    		return 0;
    	}
    	end = str.find(delim, start+delim.length());
    	str.erase(start, end+delim.length());
    	cout << str;
    	return 0;
    }
    is: "This is test!"(without quotes)?
    I expected that characters between ',' (including them) would be removed.
    Gotta love the "please fix this for me, but I'm not going to tell you which functions we're allowed to use" posts.
    It's like teaching people to walk by first breaking their legs - muppet teachers! - Salem

  2. #2
    C++ Witch laserlight's Avatar
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    The reason is that the erase() member function of std::string usually uses iterators. In your case, you are using the version that is index-based. This version takes a starting index, followed by the number of characters to erase.

    You could simply switch to the iterator version:
    Code:
    str.erase(str.begin() + start, str.begin() + end + delim.length());
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    Registered User Micko's Avatar
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    Or to use this:
    Code:
    str.erase(start, end+delim.length()-start);
    Thanks laserlight, I didn't pay attention when reading documentation.
    Gotta love the "please fix this for me, but I'm not going to tell you which functions we're allowed to use" posts.
    It's like teaching people to walk by first breaking their legs - muppet teachers! - Salem

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