Question

To practice using pointers and arrays i’m trying to do a simple program capable of converting a binary input to denary.. i think i have a good idea for the logic but i haven’t even got round to trying to implement it because im struggling to get my for loop running!

It seems silly but i know the code inside the for loop works fine outside of it, so it must be something wrong with the condition..? im trying to start at the back of the char array (navigating using pointers) and output each char(as an int) up to the first element.

So the desired output is “0 – 1 – 0 – 1 -“

#include <iostream>

using std::cout;
using std::endl;

//prototypes
void binaryToDenary(const char* input, int& inputLength);

int main(){

    const char binaryInput[] = {1,0,1,0};
    int inputLength = sizeof(binaryInput)/sizeof(binaryInput[0]);

    binaryToDenary(binaryInput, inputLength);

    return 0;
}
void binaryToDenary(const char* input, int& inputLength){
    //testing some stuff--- this all works as expected
    //cout << input[2] << " " << (int)*(input+2) << " " << inputLength <<endl;

    int i;
    for(i = inputLength; i < 0; i--){
        cout << (int)*(input+i) << " - ";
    }

}

Answer 1

Your for loop should be this:

for(i = inputLength -1 ; i  >= 0; i--)
{
    cout << (int)*(input+i) << " - ";
}

There are two problems in your code:

• i = inputLength which should be i = inputLength -1
• i < 0 which should be i >= 0

---

Also, change the second parameter type from int & to int:

void binaryToDenary(const char* input, int inputLength) //now its better!

The type int& reduces the use cases, and benefits almost nothing. If you use int &, then all of these would give compilation error:

const int inputLength = sizeof(binaryInput)/sizeof(binaryInput[0]);
^^^^ note this

binaryToDenary(binaryInput, inputLength); //compilation error
binaryToDenary(binaryInput, sizeof(binaryInput)/sizeof(binaryInput[0])); //error
binaryToDenary(binaryInput, 4); ////compilation error

So use int, and all of the above would compile fine!