add words in a string array

Question

I am trying to read a file with separate columns and including each word of a column in an array. Some of them are numeral, other literals. For the literals, I am always getting and error of type conversion. Any idea? Here follows the code:

#include <iostream>
#include <fstream>
#include <cmath>

int main ()
{
    string line; 
    int a=100;
    ifstream data;
    data.open("filename.txt");
    getline(data,line);

    int number[a];
    const char *at[3][a];
    const char *rt[3][a];
    int rn[a];

    for (int j=0;j<a;j++)
    {
        number[j] = stoi(line.substr(6,6));
        at[j] = line.substr(13,2);
        rt[j] = line.substr(13,2);
        rn[j] = stoi(line.substr(22,4));
        getline(pdb,line);
    } 
    return 0;
}

I appreciate any help!

Please correctly indent your code, that should be a better starting point! — wiredolphin
– wiredolphin, Commented Jan 2, 2016 at 22:13
substr returns a std::string. You cannot assign that to an array of char pointers (or whatever those variables are supposed to be). — Bo Persson
– Bo Persson, Commented Jan 2, 2016 at 22:17

Cheers and hth. - Alf · Accepted Answer · 2016-01-02 22:30:20Z

3

A std::string is not a char const*. Use array item type std::string instead of const char*. You need to include the <string> header. Also include <vector>, and use std::vector instead of those raw arrays. Do note that the declaration int number[a] is non-standard, it uses a g++ language extension (namely C99 variable length arrays). Using std::vector you therefore also get more portable code.

E.g., instead of

int number[a];    // Non-standard

write

vector<int> number( a );

There are more details that could be mentioned, but it's unclear what's by design here and what's due to misunderstandings. So, if there's still a problem after making the transition to std::string and std::vector, I suggest making a new question instead of amending this one.

answered Jan 2, 2016 at 22:30

Cheers and hth. - Alf

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3 Comments

RicardoCFB Over a year ago

Thanks a lot Cheers! My biggest problem is to find a way to iteratively generate an array of words collected by reading a specific column. After declaring a string array (instead of a char array), how do I add new words to this string array? Should I declare it as "string at[a];"?

Cheers and hth. - Alf Over a year ago

Like vector<string> at(a). Except it could be a good idea to change the name to something more self-describing. And also because std::vector has a member function named at, so use of that name could be confusing.

RicardoCFB Over a year ago

Solved! Thanks again Cheers!

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