Erase from string

[coll97]

I just need to get the second word of a string, for example if the string is:

string comanda = "Hello world"

And I only want "world", all I have to do is:

- comanda=comanda.substr(comanda.find_first_of(" \t")+1);

But if the string is = "Hello world" and I don`t know the number of blankspaces that can have.

Thanks

[integralfx]

comanda.erase( comanda.begin( ), comanda.find_first_of(" ") );

"Hello" and "world" is separated by a space(" ") not a space and a tab.

http://www.cplusplus.com/reference/string/string/erase/

[cire]

Here's one way:

#include <iostream>
#include <string>

std::string second_word(const std::string& s) {
    const auto npos = std::string::npos;
    const auto white_space = " \t\v\n";

    // find word break:
    auto first_ws = s.find_first_of(white_space);
    if (first_ws == npos) return std::string();

    // Find beginning of word:
    auto word_begin = s.find_first_not_of(white_space, first_ws);
    if (word_begin == npos) return std::string();

    // find next word break:
    auto word_end = s.find_first_of(white_space, word_begin);

    return s.substr(word_begin, word_end-word_begin);
}

int main() {
    const std::string strings [] = {
        "oneword",
        "two words",
        "three two one",
        "four   three   two one"
    };

    for (auto&s : strings)
        std::cout << "The second word in \"" << s << "\" is \"" << second_word(s) << "\"\n";
}

While it's not difficult to fix, this code will report the first word as the second word if any whitespace precedes the first word.

"Hello" and "world" is separated by a space(" ") not a space and a tab.

Not relevant, you have a misconception about what std::string::find_first_of does.

[integralfx]

Not relevant, you have a misconception about what std::string::find_first_of does.

Searches the string for the first character that matches any of the characters specified in its arguments.

You're right about that. My bad.