got bitten by rand() % count again

Old Habits Die Hard (OHDH)

Coming from a C background, and having to work with hash buckets often, I'm a big fan of the modulus. If you have a key that you need to map to a number where the number is potentially smaller than the value of the key, you just modulus the key, right?
So when the number is generated randomly, I'm used to this code a lot:

int slot = rand() % size;

where size would be some kind of an array that probably is bounded by "size".

However, the rand() functions in perl, java,ruby do not work like this.

perl: rand() returns a floating point number between 0 and 1.
java: rand() returns the full range of the int, including negative numbers, so the modulus gets whacked.
php: ah, just like the C library implementation!
ruby: similar to perl, rand() returns a floating point number between 0 and 1.

so there are other variations of rand() functions that you can use in these language/libraries. for java we can use:

int num = new Random.nextInt(size);

this returns numbers >= 0 and < size

perl is similar.