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invalid array subscript

May 26, 2014 at 5:53pm
D3CIM8OR (14)
I am creating a binary to ASCII converter. The way the program works is it accepts a string input, converts it to an array of ints, and converts it to ascii. The input part of the code isn't working, though:

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  string theString;
  cin >> theString;
  const int stringLength = strlen(theString.c_str());
  int intString[stringLength];


My compiler (Visual Studio Express 2013) gives me these error messages:

error C2057: expected constant expression

error C2133: 'intString' : unknown size

error C2466: cannot allocate an array of constant size 0
May 26, 2014 at 6:10pm
Peter87 (11251)
The length of the array has to be known at compile time. Either allocate the array with new or use std::vector.
May 26, 2014 at 6:42pm
closed account (j3Rz8vqX)
It works for me:
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#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;

int main()
{
    //Your stuff:
    string theString;
    cin >> theString;
    int stringLength = strlen(theString.c_str());
    int intString[stringLength];
    int value=0;

    //Inserting integer values into array:
    for(int i=0;i<stringLength;++i)
        intString[i] = theString[i]-'0';

    //Converting string integer into single string value.
    for(int i=stringLength-1;i>=0;--i)
        if(intString[i])
            value+=pow(2,stringLength-(i+1));

    //Display value as integer:
    cout<<"The integer value: "<<value<<endl;

    //Display value as character:
    cout<<"The ASCII character: "<<char(value)<<endl;

    //Custom Exit:
    cout<<"\nPress enter to continue: ";
    cin.ignore(255,'\n');
    cin.clear();
    cin.get();
    return 0;
}
 
10101010
The integer value: 170
The ASCII character: ¬

Press enter to continue:
Edit & run on cpp.sh


But I do not believe this to be standard(C++) and will not work with all compilers. http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Variable-Length.html#Variable-Length

An alternative would be:
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#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;

int main()
{
    //Your stuff:
    string theString;
    cin >> theString;
    int stringLength = strlen(theString.c_str());
    int *intString = new int[stringLength];
    int value=0;

    //Inserting integer values into array:
    for(int i=0;i<stringLength;++i)
        intString[i] = theString[i]-'0';

    //Converting string integer into single string value.
    for(int i=stringLength-1;i>=0;--i)
        if(intString[i])
            value+=pow(2,stringLength-(i+1));

    //Display value as integer:
    cout<<"The integer value: "<<value<<endl;

    //Display value as character:
    cout<<"The ASCII character: "<<char(value)<<endl;

    //Free memory:
    delete []intString;

    //Custom Exit:
    cout<<"\nPress enter to continue: ";
    cin.ignore(255,'\n');
    cin.clear();
    cin.get();
    return 0;
}
 
11111111
The integer value: 255
The ASCII character:  

Press enter to continue:
Edit & run on cpp.sh
Last edited on May 26, 2014 at 7:01pm
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