为什么c ++字符串标记生成器不起作用

Question

I tried to write a simple std::string tokenizer in c++, and I can't get it to work quite right. I found one online which does work, and I understand why it works.... but I still can't figure out why my original one isn't working. I'm assuming its some stupid little thing that I'm missing.... I'd appreciate a pointer in the right direction; thanks!

input (random character and symbols with "\\n" "\\t"):

"This is a test string;23248h> w chars, aNn, 8132; ai3v2< 8&G,\nnewline7iuf32\t2f,f3rgb, 43q\nefhfh\nu2hef, wew; wg"

tokenizer:

size_t loc, prevLoc = 0;
while( (int)(loc = theStr.find_first_of("\n", prevLoc) ) > 0) {
    string subStr = theStr.substr(prevLoc, loc-1);        // -1 to skip the \n
    cout << "SUBSTR: '" << subStr << "'" << endl << endl;
    tokenizedStr->push_back( subStr );
    prevLoc = loc+1;
} // while

output:

SUBSTR: 'This is a test string;23248h> w chars, aNn, 8132; ai3v2< 8&G'

SUBSTR: 'newline7iuf32  2f,f3rgb, 43q
efhfh
u2hef, wew; wg'

SUBSTR: 'efhfh
u2hef, wew; wg'

Notice that the second "SUBSTR" (apparently) still has the newline characters ("\\n") in it

Compilable code:

#include <vector.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>

using namespace std;

int main(int argc, char *argv[]) {

    string testStr = "This is a test string;23248h> w chars, aNn, 8132; ai3v2< 8&G,\nnewline7iuf32\t2f,f3rgb, 43q\nefhfh\nu2hef, wew; wg";
    vector<string> tokenizedStr;

    size_t loc, prevLoc = 0;
    while( (int)(loc = testStr.find_first_of("\n", prevLoc) ) > 0) {
        string subStr = testStr.substr(prevLoc, loc-1);        // -1 to skip the \n                                                                                                     
        cout << "SUBSTR: '" << subStr << "'" << endl << endl;
        tokenizedStr.push_back( subStr );
        prevLoc = loc+1;
    } // while                                                                                                                                                                        

    return 0;
}

Answer 1

The second argument of substr is a size, not a location. Instead of calling it like this:

testStr.substr(prevLoc, loc-1);

Try this:

testStr.substr(prevLoc, loc-prevLoc);

Once you fix that, the next problem you will run into is that you are not printing the last substring, because you are stopping once you don't find the newline. So from the point of the last newline to the end of the string doesn't get stored.