need help w/ number converter prog.

This program is suppoded to get an input of any number in any number system with a base from 2(binary) to 62, which includes all digits plus all capital and then all lower case letters.

Code:

---

#include <iostream>
#include <string>
using namespace std;

string relet (int input)
{
    string output;
    if (input == 0)
      output="0";
    if (input == 1)
      output="1";
// ect, ect, ect.
    if (input == 61)
      output="z";
    return output;
}

int unlet (string input)
{
    int output;
    if (input == "0")
      output=0;
    if (input == "1")
      output=1;
//ect, ect, ect.
    if (input == "z")
      output=61;
    return output;
}

int main ()
{
    string number;
    int base;
    int newbase;
// (removed for space) This part gets user input for number, base, and newbase.
    const int length=number.length();
    int input[length];
    int * output;
    output[0]=0;
// This loop puts the number into array "input", while reversing the numbers
// and replaces letters with their decimal number equivilents
    int x=0;
    int y=length-1;
    string buffer;
    start1:
    buffer=number[y];
    input[x]=unlet (buffer);
    x++;
    y--;
    if (x != length)
      goto start1;
    y=0;
    x=0;
   
   
//  -THE IMPORTANT PART-
   
// subtracts 1 from the input
    substart:
    if (input[x] == 0)
    {
      input[x]=base-1;
      x++;
      if (x == length) // end if the input is 0
          goto finish;
      goto substart;
    }
    input[x]--;
    x=0;
   
// adds 1 to the output
    addstart:
// this adds another digit to the output when nessecary
    if (x > y)
    {
      output = new int;
      output[x]=0;
      y++;
    }
    if (output[x] == newbase-1)
    {
      output[x]=0;
      x++;
      goto addstart;
    }
    output[x]++;
    x=0;
    goto substart;
    finish:
   
//(removed) outputs the "output" array starting from the top down and uses the
//"relet" function.

---

It works sometimes, but if the output is more than 2 digits it will sometimes add 1 to the second digit, and it crashes if the output is more than 4 digits long.

I have gone through the code countless times and cannot figure out what is making it not work. I can post the full code it anyone wants.

>> int * output;
>> output[0]=0

I'm not sure how you got the code to compile with that missing semicolon, but even with it there you are accessing memory that doesn't belong to you since output is uninitialized.

The semicolon is there, I just accidentally deleted it when trimming down the code. I just put it back in.
And I dont know what you mean by it isnt initialized- isnt it initialized in the line above? Plus the compiler would not let it compile if it wasnt initialized.

I don't think you should be doing this:

Code:

---

const int length=number.length();
    int input[length];

---

length is not known at compile-time, therefore you should allocate memory dynamically.

Code:

---

    int * output;
    output[0]=0;

---

output is a pointer to a single integer, not an array.

P.S If you are allowed to use std::string, could you also use a std::vector?

The array always turns out to be the right length, so even if I do change it, it isnt the scource of the problem.

I read a tutorial somewhere that said if you used the "new" operator with a pointer, you could access the locations like it was an array, or like *(output+1). Am I misunderstanding how that works?

And yes, I can use vectors

Quote:

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Originally Posted by Dash_Riprock

The array always turns out to be the right length, so even if I do change it, it isnt the scource of the problem.

I read a tutorial somewhere that said if you used the "new" operator with a pointer, you could access the locations like it was an array, or like *(output+1). Am I misunderstanding how that works?

---

Yes, that is so. But in this line:

Code:

---

output = new int;

---

you are just allocating a single integer again, and go on using it like an array. If you want an array, allocate an array:

Code:

---

output = new int[HowMany];

---

However, if you are allocating memory with new, you should also free it with delete, before the pointer goes out of scope or you intend to point it to something else.

And if you can use std::vector<int> instead, you could be almost sure none of your problems are caused by handling arrays and memory incorrectly. Which would let you concentrate on the task on hand, that is numeric conversions.

I tried it with a vector and it works perfectly after the first try. Thanks alot.