rvs 0.5.0

A library for defining and evaluating random variables using a simple DSL
Documentation 
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use crate::transform::CrateRng;

use std::fmt;

#[derive(Clone)]
pub struct ExprData {
    pub prev: u32,
    pub done: bool,
}

impl Default for ExprData {
    fn default() -> ExprData {
        ExprData {
            prev: 0,
            done: false,
        }
    }
}

pub trait Expr: fmt::Display + ExprClone {
    fn next(&mut self, rng: &mut CrateRng) -> u32;

    fn prev(&self) -> u32 {
        self.data().prev
    }

    fn done(&self) -> bool {
        self.data().done
    }

    fn data(&self) -> &ExprData;
}

/// Used to implement clone for all implementors of Expr trait.
///
/// <https://stackoverflow.com/a/30353928>
pub trait ExprClone {
    fn clone_box(&self) -> Box<dyn Expr>;
}

impl<T> ExprClone for T
where
    T: 'static + Expr + Clone,
{
    fn clone_box(&self) -> Box<dyn Expr> {
        Box::new(self.clone())
    }
}

impl Clone for Box<dyn Expr> {
    fn clone(&self) -> Box<dyn Expr> {
        self.clone_box()
    }
}