Implementation of the delimited continuations (called "Thermometer Continuations") from the paper "Capturing the Future by Replaying the Past" in Javascript.
Translated from: https://github.com/jkoppel/thermometer-continuations
The paper: https://arxiv.org/abs/1710.10385
Todo:
- Translate Typescript implementation to Javascript
- More examples
- Implement algebraic effects in Javascript
- Improve Typescript algebraic effects
const {
Thermo,
Represent,
delim,
Monad,
reflect,
} = require('./thermo');
// Monads
const arrBind = (l, f) => {
const r = [];
for(let i = 0; i < l.length; i++) {
const n = f(l[i]);
for(let j = 0; j < n.length; j++) {
r.push(n[j]);
}
}
return r;
};
const arrMonad = Monad(x => [x], arrBind);
const maybeMonad = Monad(x => x, (m, f) => m === null? m: f(m));
const stateRet = x => s => [x, s];
const stateBind = (x, f) => s => {
const [iv, is] = x(s);
return f(iv)(is);
};
const get = s => [s, s];
const put = x => s => [null, x];
const modify = f => s => [f(s), s];
const st = new Represent(stateRet, stateBind);
const stateMonad = Monad(stateRet, stateBind);
// Delimited continuations
const c = new Thermo();
const test = 1 + c.reset(() => 2 * c.shift(k => k(10)));
console.log(test); // 21
// Simple delimited continuations
const test_simple = 1 + delim((_, call) => 2 * call(10));
console.log(test_simple); // 21
const test_simple2 = 1 + delim(shift => 2 * shift(k => k(10)));
console.log(test_simple2); // 21
const test_simple3 = 1 + delim(shift => 2 * shift(k => 10));
console.log(test_simple3); // 11
// Nondeterminism (List monad)
const test2 = reflect(arrMonad, $ => $([1, 2, 3]) * $([4, 5, 6]));
console.log(test2); // [ 4, 5, 6, 8, 10, 12, 12, 15, 18 ]
// Optional (Maybe monad)
const test3 = reflect(maybeMonad, $ => $(3) + $(2) * $(4));
console.log(test3); // 11
const test4 = reflect(maybeMonad, $ => $(3) + $(null) * $(4));
console.log(test4); // null
// Mutable state (State monad)
const test5 = reflect(stateMonad, $ => $(get) + $(get)); // x <- get; y <- get; return x + y
console.log(test5(10)); // [ 20, 10 ]
const test6 = reflect(stateMonad, $ => {
const x = $(get);
$(put(100));
return x + $(get);
}); // x <- get; put 100; y <- get; return x + y
console.log(test6(10)); // [ 110, 100 ]import Thermo, { delim } from './Thermo';
import { reflect } from './Monad';
import { ListMonad, ListC, list, listProgram } from './List';
import { MaybeMonad, MaybeC, nothing, just, maybeProgram } from './Maybe';
import State, { StateMonad, StateC, get, put, stateProgram } from './State';
import { op, handle, effProgram } from './Eff';
// Delimited continuations
const c = new Thermo<number>();
const test = 1 + c.reset(() => 2 * c.shift(k => k(10)));
console.log(test); // 21
// Simple delimited continuations
const test_simple = 1 + delim<number>((_, call) => 2 * call(10));
console.log(test_simple); // 21
const test_simple2 = 1 + delim<number>(shift => 2 * shift(k => k(10)));
console.log(test_simple2); // 21
const test_simple3 = 1 + delim<number>(shift => 2 * shift(k => 10));
console.log(test_simple3); // 11
// Maybe monad
const test2 = reflect<MaybeC, number>(MaybeMonad, $ =>
$(just(1)) + $(just(2)));
console.log(''+test2); // Just(3)
const test3 = maybeProgram($ =>
$(just(1)) + $(nothing<number>()));
console.log(''+test3); // Nothing
// List monad
const test4 = reflect<ListC, number>(ListMonad, $ =>
$(list(1, 2, 3)) * $(list(4, 5, 6)));
console.log('' + test4); // [ 4, 5, 6, 8, 10, 12, 12, 15, 18 ]
const test4p = listProgram($ =>
$(list(1, 2, 3)) * $(list(4, 5, 6)));
console.log('' + test4p); // [ 4, 5, 6, 8, 10, 12, 12, 15, 18 ]
// State monad
const test5 = State.from(reflect<StateC<number>, number>(StateMonad<number>(), ($: <R>(val: State<number, R>) => R) =>
$(get()) + $(get())));
console.log(test5.eval(10)); // 20
const test6 = stateProgram<number>($ => {
const x = $(get());
$(put(1));
return x + $(get());
});
console.log(test6.eval(10)); // 11
// algebraic effects and handlers (with untyped operations)
/*
x <- flip ();
y <- flip ();
return x || y
*/
const test7 = effProgram<boolean>($ => $(op('flip')) || $(op('flip')));
const handled = handle<boolean, boolean>({
ops: {
flip: (_, k) => k(Math.random() > 0.5),
},
}, test7);
console.log(handled); // true OR false
// algebraic effects with typed operations
type Flip = {
flip: Sig<null, boolean>;
};
const test8 = effTProgram<Flip, boolean>($ => $(opT('flip', null)));
const handled2 = handleT<Flip, boolean, boolean>({
ops: {
flip: (v, k) => k(true),
},
}, test8);
console.log(handled2); // true
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