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// TODO: reduction could be made faster using higher-order reduction (see my infinite-apply implementation)
importScripts("common.js");
let MAX = 0;
let depth = 0;
let canceled = false;
const cancelReduction = () => {
if (depth++ > MAX && !canceled) {
MAX **= 1.4;
if (
!confirm(
`This takes awfully long (${depth} steps!). The reduction potentially won't converge to a valid screen (or at all!). Do you want to continue?\nWarning: This might crash your browser!`,
)
) {
canceled = true;
return true;
}
}
return canceled;
};
const incCache = {};
const inc = (i, t) => {
if (cancelReduction() || t === null) {
error("in inc");
return null;
}
if (t.hash in incCache && i in incCache[t.hash]) return incCache[t.hash][i];
let newT;
switch (t.type) {
case "idx":
newT = idx(i <= t.idx ? t.idx + 1 : t.idx);
break;
case "app":
newT = app(inc(i, t.left))(inc(i, t.right));
break;
case "abs":
newT = abs(inc(i + 1, t.body));
break;
case "def":
error("unexpected def");
return null;
}
if (!(t.hash in incCache)) incCache[t.hash] = {};
incCache[t.hash][i] = newT;
return newT;
};
const substCache = {};
const subst = (i, t, s) => {
if (cancelReduction() || t === null) {
error("in subst");
return null;
}
const h = hash("" + t.hash + s.hash);
if (h in substCache && i in substCache[h]) return substCache[h][i];
let newT;
switch (t.type) {
case "idx":
newT = i == t.idx ? s : idx(t.idx > i ? t.idx - 1 : t.idx);
break;
case "app":
newT = app(subst(i, t.left, s))(subst(i, t.right, s));
break;
case "abs":
newT = abs(subst(i + 1, t.body, inc(0, s)));
break;
case "def":
error("unexpected def");
return null;
}
if (!(h in substCache)) substCache[h] = {};
substCache[h][i] = newT;
return newT;
};
// guaranteed normal form
// only use if sure that t is not a (potentially diverging) screen
const gnf = (t) => {
if (cancelReduction() || t === null) {
error("in gnf");
return null;
}
switch (t.type) {
case "app":
const _left = gnf(t.left);
if (_left === null) return null;
return _left.type === "abs"
? gnf(subst(0, _left.body, t.right))
: app(_left)(gnf(t.right));
case "abs":
return abs(gnf(t.body));
case "def":
error("unexpected def");
return null;
default:
return t;
}
};
// weak head normal form
const whnfCache = {};
const whnf = (t) => {
if (cancelReduction() || t === null) {
error("in whnf");
return null;
}
if (t.hash in whnfCache) return whnfCache[t.hash];
switch (t.type) {
case "app":
const _left = whnf(t.left);
if (_left === null) return null;
newT =
_left.type === "abs"
? whnf(subst(0, _left.body, t.right))
: app(_left)(t.right);
break;
case "def":
error("unexpected def");
return null;
default:
newT = t;
break;
}
whnfCache[t.hash] = newT;
return newT;
};
// screen normal form
// one of [((((0 tl) tr) bl) br)], [[0]], [[1]]
const snfCache = {};
const snf = (_t) => {
if (_t !== null && _t.hash in snfCache) return snfCache[_t.hash];
let t = whnf(_t);
if (t === null || t.type !== "abs") {
error("not a screen/pixel");
return null;
}
t = abs(whnf(t.body));
if (t.body.type === "abs") return gnf(t); // not a screen, probably a pixel
while (t !== null && !seemsScreeny(t)) {
// TODO: a bit unsure about this
switch (t.type) {
case "app":
const _left = whnf(t.left);
t =
_left.type === "abs"
? subst(0, _left.body, t.right)
: app(_left)(whnf(t.right));
break;
case "abs":
t = abs(whnf(t.body));
break;
case "def":
error("unexpected def");
return null;
default:
error("type");
return null;
}
}
snfCache[_t.hash] = t;
return t;
};
let running = false;
const stack = [];
const reduce = () => {
running = true;
for (let i = 0; stack.length > 0; i++) {
// console.log(i, stack.length);
let [{ ctx, t }] = stack.splice(
Math.floor(Math.random() * stack.length),
1,
);
// let { ctx, t } = stack.shift();
// let { ctx, t } = stack.pop();
// TODO: priority queue on context size
if (toColor(t) !== UNKNOWN) continue;
// could loop in gnf, therefore limit depth
MAX = 1000000;
depth = 0;
canceled = false;
try {
t = snf(t);
} catch (e) {
error(e);
return null;
}
if (t === null) {
error("in reduce");
return null;
}
// smaller resolutions apparently crash the browser tab lol
if (ctx.x[1] - ctx.x[0] < 3) continue;
postMessage({ ctx, t });
}
running = false;
};
self.onmessage = (msg) => {
stack.push(msg.data);
if (!running) reduce();
};
|
