Thread: Can anyone explain to me why my function is not working...?

What am I missing in my logic?

Code:

int currentIndexOfSearchString = 0;
        for (int i = 0; i < sourceStringSize; i++) {
             if (sourceString[i] == searchString[0]) { //then we have now found the first character of the searchString in the sourceString
                 for (int i2 = i; i2 < sourceStringSize && i2 < searchStringSize; i2++) {
                      if (sourceString[i2] != searchString[currentIndexOfSearchString]) {
                          if (i2 == searchStringSize - 1) { //we're at the last character of the searchString
                              return false;
                          }
                             
                          else {
                              if (i2 < sourceStringSize - searchStringSize) { //meaning we have enough characters in sourceString to store a possible match of searchString
                                  i = i2; //set the outer for loop iterator to the value of the inner one
                                  break; //out of this loop at the first char of the sourceString that doesn't match the current char of the searchString
                              }
                              else {
                                  return false;
                              }
                          }               
                      }
                      else {
                          //we're good so far...
                      }
                      currentIndexOfSearchString++; //increment to the next character index in the searchString
                 }
 
             }  
        }

Obviously I need another "return false" line in there somewhere, but I have no idea where to put it.

Current source code:
C++ code - 284 lines - codepad

Are you trying to write a version of strstr() for practice or such? If not, there are functions you can use to make your life simpler if you are using the string class.

Originally Posted by syzygy

Are you trying to write a version of strstr() for practice or such? If not, there are functions you can use to make your life simpler if you are using the string class.

Functions such as what?
I don't know of any function in the string class for checking to see if one string contains another string (there is string::find(), but that returns the position of the string in the string, and I just want to know if one string contains another string). That's why I'm writing my own.

Like I mentioned, strstr() will find a string within another string.

there is string::find(), but that returns the position of the string in the string, and I just want to know if one string contains another string

O_o

If you know this, and this isn't a learning exercise, why on earth aren't you using `std::string::find' to implement this?

Soma

Originally Posted by syzygy

Like I mentioned, strstr() will find a string within another string.

And, like I mentioned, I need a function which returns a bool value to indicate whether or not one string contains another string.

Why a bool? Can you not convert the logic of "if this is null, it's false, otherwise it's true" yourself?

Originally Posted by syzygy

Why a bool? Can you not convert the logic of "if this is null, it's false, otherwise it's true" yourself?

Yes I can, but its easier using bool values.

Originally Posted by prog-bman

So this:

Code:

void somefunc()
{
    bool containsString = str.find("awesome") != std::string::npos;
}

is not as good as this:

Code:

bool ContainsString(string x, string y)
{
    //Insert bunch of custom code here

    return contains;
}
void somefunc()
{
    bool containsString = ContainsString(str, "awesome");
}

Hahaha...yeah, I see your point. But what would be the fun in that...?