AAAAAAAAAAA C++ sucks

[w00tw00tkab00t]

C is so much better.

But what i came here to do:

I wrote this base conversion program in C. I was going to use it for encryption.... (not just base conversion, but that's a part of the algorithm). Today i tried porting it to C++. I have absolutely no clue what's wrong with it, but any help would be appreciated.

Sorry for the lack of comments, if you want an explanation about a certain part just post here and i'll explain.

Compile with 'g++ -o btob btob.cpp' (or whatever compiler you use / whatever file you choose to save it as).
It compiles fine, screws up running........ no error message. and gdb isn't helping me this time.

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

char toch(int w) {
  if (w > 9) return (w + 55);
  else return (w + 48);
}

int toi(char w) {
  if (w > 64) return (w - 55);
  else return (w - 48);
}

string revstr(string str) {
  char tmp;
  int l = str.length(), l2 = l - 1, ong;
  for (ong = 0; ong < (l / 2); ong ++) {
    tmp = str[ong];
    str[ong] = str[l2 - ong];
    str[l2 - ong] = tmp;
  }
  return str;
}

string itob(int n, int r) {
  string blah;
  int m;
  char tmp;
  int l, l2, ong;
  for (m = 0; (n % (int)pow((float)r, (float)m)) != n; m++) {
    blah[m] = toch((n % (int)pow((float)r, (float)(m + 1))) / (int)pow((float)r, (float)m));
    n -= n % (int)pow((float)r, (float)(m + 1));
  }
  blah[m + 1] = toch((n % (int)pow((float)r, (float)(m + 1))) / (int)pow((float)r, (float)m));
  return revstr(blah);
}

int btoi(string num, int r) {
  int l = num.length(), ans = 0, ong;
  for (ong = 1; l - ong >= 0; ong++)
    ans += toi(num[l - ong]) * (int)pow((float)r, (float)(ong - 1));
  return ans;
}

int main() {
  int b1, b2;
  string num;
  cout << "FIRST BASE? ";
  cin >> b1;
  cout << "SECOND BASE? ";
  cin >> b2;
  cout << "NUMBER? ";
  cin >> num;
  cout << itob(btoi(num, b1), b2) << endl;
  return 0;
}

And here's the WORKING version in C:
(compile with 'gcc -lm -o btob btob.c'.... replace names as needed)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

char toch(int w);
int leng(char* str);
void revstr(char* str);
char* itob(int n, int r);
int btoi(char* num, int r);

char toch(int w) {
	if (w > 9) return (w + 55);
	else return (w + 48);
}

int toi(char w) {
	if (w > 64) return (w - 55);
	else return (w - 48);
}

int leng(char* str) {
  int x;
  for (x = 0; str[x] != 0; x++) {}
  return x;
}

void revstr(char* str) {
  char tmp;
  int l = leng(str), l2 = l - 1, ong;
  for (ong = 0; ong < (l / 2); ong++) {
    tmp = str[ong];
    str[ong] = str[l2 - ong];
    str[l2 - ong] = tmp;
  }
}

char* itob(int n, int r) {
	char* tmpstr = malloc(sizeof(char) * 1024);
	int m;
	for (m = 0; (n % (int)pow(r, m)) != n; m++) {
		tmpstr[m] = toch((n % (int)pow(r, m + 1)) / (int)pow(r, m));
		n -= n % (int)pow(r, m + 1);
	}
	tmpstr[m+1] = toch((n % (int)pow(r, m+1)) / (int)pow(r, m));
	revstr(tmpstr);
	return tmpstr;
}

int btoi(char* num, int r) {
	int l = leng(num), ans = 0, ong;
	for (ong = 1; l - ong >= 0; ong++) {
		ans += toi(num[l - ong]) * (int)pow(r, ong - 1);
	}
	return ans;
}

int main() {
  char num1[20];
  int b1, b2;
  printf("FIRST BASE? ");
  scanf("%d", &b1);
  printf("FIRST NUM? ");
  scanf("%s", num1);
  printf("SECOND BASE? ");
  scanf("%d", &b2);
  printf("%s\n", itob(btoi(num1, b1), b2));
  return 0;
}

Sorry for the incredibly long-ish post.

P.S. if you decidce you want to use my base conversion algorithm for some reason, and copy it instead of writing your own.... please give me a little credit. I know this is a pretty insignificant program but it was hard for me to write.

[7stud]

That is about the worst program style I've ever seen. Change all your variable names to something meaningful, and whatever you do, don't ever use variable names like "l" that look like the numeral 1.

[w00tw00tkab00t]

yeah, i was being lazy.
l was for length.
ong was random... i was looking for something to indicate continuation of a loop, ong = short for ongoing.

any idea how to fix the problem though?

[SlyMaelstrom]

What was "blah" short for I wonder. Make it more readable, then people will be more interested in helping you.

[w00tw00tkab00t]

blah was just there.
since nobody wants to read through my horrible code, let me ask:
about strings in C++..... when you pass a string to a function is it just giving you a pointer to the first element?

[SirCrono6]

It will pass the entire string. It's an object, so of course it will pass like that.

[w00tw00tkab00t]

hmm i was stepping through it with gdb..... and when i found there was a problem (I think) in itob (Integer TO Base) with "string blah;" i tried doing "string blah = new string;" and got this compilation error:

btob.cpp: In function ‘std::string itob(int, int)’:
btob.cpp:27: error: conversion from ‘std::string*’ to non-scalar type ‘std::basic_string<char, std::char_traits<char>, std::allocator<char> >’ requested

i think that's it, so umm... yeah. what should i do to fix that error?

[SlyMaelstrom]

You don't allocate memory into data, you allocate into pointers.

string *blah = new string;

...and I don't think that's your problem.

[w00tw00tkab00t]

hmm....
this is really confusing.

[CornedBee]

You realize your C version leaks memory, do you?

What you don't realize is that std::string has a fixed size at any single point, although it can grow. What this means is that you can't use [] to access a non-existent index. This is exactly what you try in itob, though. You need to resize the string first.

[7stud]

hmm....
this is really confusing.

new returns an address in memory. In C++, addresses in memory are stored in variables that are pointers. Therefore, when you use new on the right of an assignment statement, there has to be an appropriate pointer type on the left side of the assignment.

[w00tw00tkab00t]

how does my C version 'leak memory' and how can i prevent it?

also, how do i resize a string?

thanks for the help

[CornedBee]

how does my C version 'leak memory' and how can i prevent it?

You allocate memory here:

char* tmpstr = malloc(sizeof(char) * 1024);

but never free it. (You also allocate far more than can ever be needed - the longest possible string to be created by itob is sizeof(int)*CHAR_BIT characters long, which on no platform I ever heard of is greater than 40, so 41 is the limit you need to allocate.) To prevent, the typical way is to pass a buffer into itob instead of returning an allocated one. This way, it's clear who is responsible for the memory. In your case, you'd have to free the pointer returned by itob eventually. The trick here lies in knowing (or rather, remembering) that itob actually allocates memory.

C++ takes these issues away. I can't help but wonder at your topic title and your first line.

also, how do i resize a string?

The easiest way is the += operator. It resizes the string as necessary.

string str = "Hello";
str += ", World!";

[talnoy]

hmm, i would help but i have no idea what any of thsi means

[w00tw00tkab00t]

well C is just so much more.... compatible and simpler. even though it's occasionally more complicated, and takes a bit more work (lack of OOP / libraries for certain functinos) i love it.

anyways..... how would i do it the not-easiest way? i'll use the += op for now though.