glaebhoerl

// Based on idea: https://twitter.com/pkhuong/status/1287510400372748290

use hashbrown::raw::RawTable;

pub struct ScopeMap<K, V> {
    last_scope_id: ScopeId,
    scopes:        Vec<ScopeId>, // values are zeroed instead of popped to save a check in get() / is_fresh()
    current_scope: ScopeDepth,   // index of innermost valid scope
    values:        RawTable<Entry<K, V>>,
    shadowed:      Vec<Shadowed<K, V>>,

glaebhoerl

-- see also previous gist https://gist.github.com/glaebhoerl/466267f0c977cef74202f167d6493cc0 and tweets https://twitter.com/glaebhoerl/status/1129851506067427329
-- here we accomplish the same thing but in a totally different way, by relying on the host language for basically everything

{-# LANGUAGE LambdaCase, GADTs, TypeOperators, DataKinds, PolyKinds, Strict, DeriveFunctor, RankNTypes, TypeFamilies, ConstraintKinds #-}

import Prelude hiding (product, sum)
import Data.Type.Equality
import GHC.Exts (Constraint)

glaebhoerl

{-# LANGUAGE LambdaCase, OverloadedStrings #-}

import Data.String

type Name = String

data Expr
    = V Name
    | Lam Name Expr
    | Either Bool Expr -- "False = Left, True = Right"

glaebhoerl

{-# LANGUAGE GADTs, DeriveFunctor, RankNTypes #-}

import Prelude hiding (Monad (..))

main = print ()

-----------------------------------------------------------------------

class Functor m => Monad m where
    return :: a                 -> m a

glaebhoerl

-- Code taken from http://stackoverflow.com/questions/12735274/breaking-data-set-integrity-without-generalizednewtypederiving/12744568#12744568
-- Discussion on haskell-cafe: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/100870
--                             http://www.haskell.org/pipermail/haskell-cafe/2012-October/103984.html
-- Modified to remove orphan instances by rwbarton
-- Simplified by glaebhoerl

module A (A(..), Set, empty, insert, on) where
import Data.Set
import Data.Function

glaebhoerl

module Person (Person, null, newPerson, isNull, getAge, getName) where

-- constructor is not exported! only this module has access to the internal Maybe
newtype Person = Person (Maybe (Int, String)) 

null :: Person
null = Person Nothing

newPerson :: Int -> String -> Person
newPerson age name = Person (Just (age, name))

glaebhoerl

{-# LANGUAGE PolyKinds, GADTs, DataKinds, TypeFamilies, TypeOperators,
  MultiParamTypeClasses, FlexibleContexts, FlexibleInstances,
  UndecidableInstances #-}

module GHC_Query where

data Proxy (t :: k) = Proxy
data KindProxy (t :: *) = KindProxy  -- a type-level proxy for kinds

data Nat = Z | S Nat

glaebhoerl

template<typename Return, typename... Arguments>
struct FnOnce
{
    using This = FnOnce<Return, Arguments...>;

    virtual Return operator ()(Arguments&&...) && = 0;
};

template<typename Return, typename... Arguments>
struct FnMut: FnOnce<Return, Arguments...>

glaebhoerl

template<typename T, T x>
struct Value
{
    static constexpr T value() { return x; }
};

template<int n>
using Int = Value<int, n>;

template<bool b>

glaebhoerl

## Exceptions
Parts:
 * union types / restricted Any
 * match-on-type
 * `throws Type`, `throw val`
 * `try!`

Union types:
  Either<A, B, C, D>
  Can be any of A, B, C, or D