The sum of all weights is 8; therefore, the probability of taking the first branch is (3/8)0.375, the probability
of taking the second is (1/8)0.125, and the probability of taking the third is (4/8)0.5.
If a branch specifies a zero weight, then that branch is not taken.
The randcase weights can be arbitrary expressions, not just constants.
In the preceding example, the first three weight expressions are computed using 8-bit precision, and the fourth
expression is computed using 12-bit precision.
Each call to randcae statement will return a random number in the range from 0 to SUM.