Really basic terrain generator

Question

This is my first attempt at writing a c++ program, so bear with me. I tried to use as many methods as I learned in about a week-long period.

#include <iostream>
#include <stdlib.h>
#include <time.h>
void generator(char tree, char water, char land)
{
 const char tileList[] = {tree, water, land};
 int tileIndex = rand() % 3;
 std::cout << tileList[tileIndex] << " ";
}
int main()
{
 srand(time(NULL));
 while(true)
 {
 generator('T', '~', '.');
 }
}

I took out comments to improve code readability. What can be improved? What needs to be changed?

• Simon Forsberg: I didn't know Putin could code...
• TemplateRex: @SimonAndréForsberg he has already too many distractions to be coding properly, although I'm sure he could pick it up if he wanted to ;-)
• Vladimir Putin: Just out of curiosity, why the downvote?

Answer 1

This won't compile:

void generator(char tree, char water, char land);
// ...
generator("T", "~", ".");

Because generator takes 3 chars, and you're giving it const char* instead.

Of course that's easy to fix, just make the params chars:

generator('T', '~', '.');

---

It would be better if the generator generated, instead of printing. It's to preserve the single responsibility principle. Like this:

char generator(char tree, char water, char land)
{
 const char tileList[] = {tree, water, land};
 int tileIndex = rand() % 3;
 return tileList[tileIndex];
}
int main()
{
 srand(time(NULL));
 while(true)
 {
 std::cout << generator('T', '~', '.') << " ";
 }
}

---

Of course the loop will never end... Are you ok with that?

---

Taking 3 chars as possible tiles doesn't seem too flexible. How about making it work with arbitrary number of tiles? Something like this:

char generator(const char * tiles, int len)
{
 int index = rand() % len;
 return tiles[index];
}
int main()
{
 srand(time(NULL));
 const char * tiles = "T~.";
 int len = strlen(tiles);
 while(true)
 {
 std::cout << generator(tiles, len) << " ";
 }
}

• Vladimir Putin: Whoops, forgot about the difference between '' and "" when copying the code over.

Answer 2

Doing rand that way is bad.

The exact value of RAND_MAX can very but is usually 32767 (or multiples thereof).
This means rand() % 3 gives you:

 0: 1/10923 // Notice that 0 and 1
 1: 1/10923 // have a slightly higher probability.
 2: 1/10922

There are all sorts of other issues with rand. So you may want to look at the new random libraries provided with C++11.

But if you want to use rand() in the most non biased way possible.

 int getRand(int max)
 {
 int max = RAND_MAX/max*max; // Note integer division
 // So /max*max does not cancel out.
 int val;
 do
 {
 val = rand();
 } while(val >= max);
 return val % max;
}

At least that will give you an even distribution.