[C++] comparison vector and array of char

robertodb · 09-20-2011, 03:09 AM

I have to write an application in which a text file is read and stored in a vector of strings

Code:

vector<string> text;

After that I have to compare each character of text loaded from a file with an array of char with default content

Code:

char ARRAY[21] = {... ... ...}

so I thought something like that

Code:

for(int i = 0; i < text.size(); i++){
               for(int j = 0; j < 21; j++){
                       if(text[i] == ARRAY[j])
                       index_t[i] = j;
               }        
       }

at compile time I get the following error:
no match for 'operator==' in '(((std::vector<std::string, std::allocator<std::string> >*)
how can I fix that?

Sylvester Ink · 09-20-2011, 03:30 AM

It seems like currently you are iterating through the vector of strings. For each string you are comparing it to each char element in the array, and if it matches keep track of which char matched in that particular string. However, currently you are comparing a string and a char, and since these elements aren't the same type, they can't be compared. Instead you would need to add another for loop to iterate through each character of the string and compare each character with the char. You could also use the find() method of the string if you just need to check if the string contains that char.

robertodb · 09-20-2011, 05:53 AM

I will be more clear: I have to compare each character of each string in vector. If the comparison is positive, I associate the array index corresponding to the letter to a variable. For example, if the character of a string in vector is 'R', the index variable assumes a value of 15, as ARRAY [15] = R.

dwhitney67 · 09-20-2011, 06:06 AM

Quote:

Originally Posted by robertodb

I will be more clear: I have to compare each character of each string in vector. If the comparison is positive, I associate the array index corresponding to the letter to a variable. For example, if the character of a string in vector is 'R', the index variable assumes a value of 15, as ARRAY [15] = R.

I think you were pretty clear the first time. So was Sylvester Ink's response, although I think he meant to indicate that you should use find_first_of(), and not find().

Code:

std::vector<std::string> text;
size_t* index_t = new size_t[text.size()];

for (size_t i = 0; i < text.size(); ++i)
{
   size_t pos = text[i].find_first_of(ARRAY);

   if (pos != std::string::npos)
   {
      index_t[i] = pos;
   }
}

...

delete [] index_t;

Refer to these links for more information on STL string:

http://www.cplusplus.com/reference/string/string/
http://www.cplusplus.com/reference/s...find_first_of/