Drive instagenerate in a probabilistic way

[siscia]

Hi Alex,

I was wonder if it is somehow possible to drive instagenerate in a probabilistic way.

Let me explain.

Let's suppose I got a grammar similar to:

A = B ('c3' | 'd4')
B = 'a1' | 'b2'

This will generate these 4 strings:

a1c3
b2c3
b2d4
a1d4

Now, for my goal, I know that is more likely that the string I am looking for start with a1, so I want the generator to return first a1c3 and a1d4 and later b2c3 and b2d4.

Is that possible ? How ?

Do you suggest some resource I can explore further ?

Thanks for your time and wonderful work :)