Assigning an integer into index in char * pointer array

Question

Redoing my previous question since I didn't provide enough detail.

I have a char pointer array, char* token[100]. Let's say I have a double-digit number, like 33.

How do I assign this int into an index in the token array, so that when I print out that token it will give me 33 and not some sort of ASCII value?

char* token[100];
int num = 33;
//How do I assign num into a specific token index, like for example:
token[1] = num;
//When I print out that token index, I want 33 to be printed out
cout << token[1] << endl; // I want to have 33 be the result. Right now I have '!' as an output

First you need to understand that a char* is a pointer to a location in memory. You have set it to the value 33, which almost certainly isn't within your program's address space. Then you are trying to read a string which you incorrectly assume is stored in that memory location and write it to standard out. — paddy
– paddy, Commented Feb 17, 2020 at 22:53
Do you know the difference between a char *[] and a char []? Do you know the difference between a char and an int? Do you know what an array is? We're asking these questions so we can direct you to the best resources. We need to gauge your level of understanding. — JohnFilleau
– JohnFilleau, Commented Feb 17, 2020 at 22:59

Vlad from Moscow · Accepted Answer · 2020-02-18 08:15:04Z

1

It seems you mean something like the following

#include <iostream>
#include <string>
#include <cstring>

int main() 
{
    char * token[100] = {};
    int num = 33;

    std::string s= std::to_string( num );

    token[1] = new char[s.size() + 1];

    std::strcpy( token[1], s.c_str() );

    std::cout << "token[1] = " << token[1] << '\n';

    delete [] token[1];

    return 0;
}

The program output is

token[1] = 33

If you are not allowed to use C++ containers and functions then the program can look the following way

#include <iostream>
#include <cstdio>
#include <cstring>

int main() 
{
    char * token[100] = {};
    int num = 33;

    char buffer[12];

    std::sprintf( buffer, "%d", num );

    token[1] = new char[std::strlen( buffer ) + 1];

    std::strcpy( token[1], buffer );

    std::cout << "token[1] = " << token[1] << '\n';

    delete [] token[1];

    return 0;
}

edited Feb 18, 2020 at 8:15

answered Feb 17, 2020 at 23:00

Vlad from Moscow

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2 Comments

madaniloff Over a year ago

Ah, thank you! That is what I meant. However, my teacher doesn't allow me to use the std:: commands, so is there a way to do this that doesn't use those?

chux Over a year ago

To handle all 32-bit int, char buffer[12]; makes more sense.

JohnFilleau · Accepted Answer · 2020-02-17 23:18:12Z

0

I'm convinced, from comments, that you want an array of integer types. If we get further clarification about why this needs to be a char array, I'll update my answer, but from all available information it seems like you really want an integer-type array.

#include <iostream>

int main(int argc, char** argv)
{
    int token[100] = {};
    int num = 33;

    token[1] = num;

    std::cout << token[1] << std::endl;

    return 0;
}

answered Feb 17, 2020 at 23:18

JohnFilleau

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5 Comments

madaniloff Over a year ago

This needs to be a char array because I am reading in an equation like this (3 + 34 x 7) and I need to basically have each number in its own array for example: token[3][+][34][x][7].

JohnFilleau Over a year ago

If your equation was 3 + 256 what tokens would be stored in the char array? A char is usually only 8 bits, so that 256 will overflow if you try to store it as a single char.

madaniloff Over a year ago

ok maybe I don't completely understand chars but I thought that 256 would be treated as a string and would just be token[256]

JohnFilleau Over a year ago

@madaniloff What is the input and output of your program? Do you need to solve the typed in equation? Because the equation 3 + 34 x 7 would be stored as the character array {3, 43, 34, 120, 7}. After storing it in an array, how can you tell which of those chars are operators and which are numbers?

madaniloff Over a year ago

Basically I am taking user input from a char, so, for example, input would be input[3][+][34][x][7]. If the number is a single digit or operator I am just assigning it to the token array like this token[i] = input[i].

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