Compile Time Boolean formula Interpreter

formula.rs

use std::marker::PhantomData;


enum Ast{};
enum Eval{};
trait Mode {}
impl Mode for Ast {}
impl Mode for Eval {}

trait Boolean{}
trait Formula{ type Output : Boolean + Formula; }

enum True{}
impl Boolean for True{}
impl Formula for True {type Output = Self;}

enum False{}
impl Boolean for False{}
impl Formula for False {type Output = Self;}

// ast
struct And<L : Formula, R : Formula, M : Mode = Ast>(core::convert::Infallible, core::marker::PhantomData<(*const M, fn(L,R))>);

// eval
impl<L: Formula, R : Formula> Formula for And<L , R> 
where 
  And<L::Output,R::Output, Eval> : Formula
{ 
  type Output = <And<L::Output,R::Output, Eval> as Formula>::Output ;
}
impl Formula for And<True , True , Eval> { type Output = True;}
impl Formula for And<False, True , Eval> { type Output = False;}
impl Formula for And<True , False, Eval> { type Output = False;}
impl Formula for And<False, False, Eval> { type Output = False;}

// ast
struct Or<L : Formula, R : Formula, M : Mode = Ast>(core::convert::Infallible, core::marker::PhantomData<(*const M, fn(L,R))>);
// eval
impl<L: Formula, R : Formula> Formula for Or<L , R>
  where Or<L::Output,R::Output, Eval> : Formula
{ 
  type Output = <Or<L::Output, R::Output, Eval> as Formula>::Output ;
}
impl Formula for Or<True , True , Eval> { type Output = True;}
impl Formula for Or<False, True , Eval> { type Output = True;}
impl Formula for Or<True , False, Eval> { type Output = True;}
impl Formula for Or<False, False, Eval> { type Output = False;}


struct Not<T : Formula, M : Mode = Ast>(core::convert::Infallible, core::marker::PhantomData<(M, fn(T))>);

impl<T:Formula> Formula for Not<T> 
  where Not<T::Output, Eval> : Formula 
{ 
  type Output = <Not<T::Output, Eval> as Formula>::Output;
}
impl Formula for Not<True, Eval>  {type Output = False;}
impl Formula for Not<False,Eval> {type Output = True;}

const fn proof<F : Formula<Output = True>>() {}

const _0 : () = proof::<Not<Not<Or<False, And<True, And<True, True>>>>>>();

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