Exercise 6.2 on page 83:
*Write a function to generate a Double between 0 and 1 , not including 1.*
The given hint and answer indicate generating a non-negative Int and then
dividing it by the one more than the maximum possible Int value.
Maybe I'm missing something, but it seems to me that since a Double is
represented using 64 bits and an Int 32, that using the amount of
randomness in an Int to generate a random Double will mean that the results
will be unevenly distributed, perhaps with possible values of the Double
never returned. Here's what I came up with:
def double(rng: RNG): (Double, RNG) = {
val (int1, rng2) = rng.nextInt
val (int2, rng3) = rng2.nextInt
val long = (int1.toLong << 32) | int2 // this is a random
Long
val nnLong = if (long < 0) -(long + 1) else long // non-negative random
Long
val rLong = -(nnLong.toDouble / Long.MinValue) // random double
(rLong, rng3)
}
I generate two random integers, convert one to a Long and bit-shift it 32
bits to the left and then OR it with the other Int. This should give me a
random Long. Then I make it non-negative, divide it by the minimum Long
value, and negate that. Intuitively this seems to me that it would give a
more even distribution since there are extra bits of randomness from the
second Int. Is my thinking correct? Is this worse or better than the
answer given in the book?
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