ClarkeRemy

datatype expr = PLUS of expr * expr 
              | NUM  of int

fun eval_expr (NUM n)      = n
  | eval_expr (PLUS (l,r)) = eval_expr l + eval_expr r

fun pretty_expr (NUM n)      = Int.toString n
  | pretty_expr (PLUS (l,r)) = "( " ^ pretty_expr l ^ " + " ^ pretty_expr r ^ " )"

ClarkeRemy

fun y f x = f (y f) x


functor Fix(type 'a f )
= struct
  type 'a f = 'a f
  datatype fix = FIX of fix f
  fun inj      v  = FIX v
  fun prj (FIX v) = v
  end

ClarkeRemy

// // if it was C :
//
// enum t {
//   Plus = 0,
//   Mul = 1,
//   num = 2,
// }
// union e { plus : Plus<*const TG>, mul : Mul<*const TG>, num : u32 }
// struct TG { tag : int, val : e }

ClarkeRemy

// this is just to satisfy the type system as I don't have the function
mod boys { pub mod micb25 { pub fn boys(_:u64,_:f64)->f64 {1.0} }}
#[derive(Clone, Copy)]
pub struct Vector3<T> {x:T,y:T,z:T}
impl Vector3<f64> {
  fn norm_squared(&self)->f64 {self.x*self.x+self.y*self.y+self.z*self.z}
}

// direct style

ClarkeRemy

use std::marker::PhantomData;


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

ClarkeRemy

// original

// fn hermite_expansion(i: i32, j: i32, t: i32, dist: f64, a: f64, b: f64) -> f64 {
//     let p = a + b;
//     let q = a * b / p;

//     if t < 0 || t > i + j {
//         0.0
//     } else if i == j && j == t && t == 0 {
//         f64::exp(-q * dist.powi(2))

ClarkeRemy

structure Plus = struct
    datatype 'a t = T of 'a -> 'a -> 'a
  end

structure Mul = struct
    datatype 'a t = T of 'a -> 'a -> 'a
  end

structure FromInt = struct

ClarkeRemy

(* direct style *)
fun substractorial n =
    if n < 0 
    then 0
    else n - substractorial (n-1)

(*  Continuation passing style *)
(*  In a functional language, when every branch is a "tail call", it optimizes to a jumps *)
(*     this could already be turned into a loop pretty easily,

ClarkeRemy

const interface_method = (object, _interface)=>(method) => (
        object._interface[_interface].hasOwnProperty(method) 
    && (typeof object._interface[_interface][method]) == "function"
)
const implInterface = (_interface, invariant, object, impl) => {
    if (!object.hasOwnProperty("_interface")) {
        object._interface = {};
    }
    object._interface[_interface] = impl
    if (!invariant(object)) {throw `FAILED TO IMPLEMENT \`${_interface}\``}

ClarkeRemy

#![allow(unused)]
use std::{borrow::Borrow, convert::Infallible};

trait Functor {
  type F<T>;
  fn fmap<A, B>(f: impl Fn(A) -> B, x: Self::F<A>) -> Self::F<B>;
}

trait Rec: Sized {
  type Fix;