Maybe

A tiny probabilist functional language

Build instructions

This repository require a recent version of OCaml to be installed. I recommend to install OCaml 4.14 via opam.

Once opam is correctly setup, the following commands should suffice to compile the project:

cd path/to/Maybe
opam install dune opal
dune build

Usage

To execute a given probabilist program written in a file <file>.maybe :

dune exec -- maybe <file>.maybe

To infer all possible results with the associated probabilities (inference) :

dune exec -- maybe -infer <file>.maybe

The language

Maybe supports conditions, let-bindings, additions and sampling over simple distributions.

Conditions

if <expr> {
  <expr>
} else {
  <expr>
}

Let

let x = <expr> in <expr>

Additions

<expr> + <expr>

Sampling

Bernouilli variable (1 with probability p and 0 with probability 1 - p).

B(p)

Uniform choice over a list of integer constants

U[<int>, ..., <int>]

Example

The following Maybe program sums to variables each following a uniform distribution.

let x = U[1, 2, 3, 4] in
let y = U[1, 2, 3, 4] in
x + y

Running maybe -infer on this program gives:

2 ~ 0.062500
3 ~ 0.125000
4 ~ 0.187500
5 ~ 0.250000
6 ~ 0.187500
7 ~ 0.125000
8 ~ 0.062500