Provides an experimental macro for expressing constraints in a 'natural' way.

With constraint macro:

import Furlong.Constraint
{x, y} = {make_ref(), make_ref()}
constraint = constraint(3*x >= y/2-5)

Without constraint macro:

import Furlong.Symbolics
{x, y} = {make_ref(), make_ref()}
constraint = gte(multiply(3, x), subtract(divide(y, 2), 5))