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/* lambda calculus */
const allHashes = {};
const hash = (s) => {
let h = 0;
for (let i = 0; i < s.length; i++) {
const chr = s.charCodeAt(i);
h = (h << 5) - h + chr;
h |= 0;
}
while (h in allHashes && allHashes[h] !== s) h += 1;
allHashes[h] = s;
return h;
};
const abs = (body) => {
if (body === null) return null;
const t = { type: "abs", body };
t.hash = hash("abs" + body.hash);
return t;
};
const app = (left) => (right) => {
if (left === null || right === null) return null;
const t = { type: "app", left, right };
t.hash = hash("app" + left.hash + right.hash);
return t;
};
const idx = (idx) => {
if (idx === null) return null;
const t = { type: "idx", idx };
t.hash = hash("idx" + idx);
return t;
};
const def = (name) => {
const t = { type: "def", name };
t.hash = hash("def" + name);
return t;
};
/* lambda screen */
const WHITE = 0;
const BLACK = 1;
const UNKNOWN = 2;
// [[1]]=w, [[0]]=b, other=g
const toColor = (t) => {
if (t.type === "abs" && t.body.type === "abs" && t.body.body.type === "idx")
return t.body.body.idx === 1
? WHITE
: t.body.body.idx === 0
? BLACK
: UNKNOWN;
return UNKNOWN;
};
// [((((0 tl) tr) bl) br)]
const seemsScreeny = (t) =>
t.type === "abs" &&
t.body.type === "app" &&
t.body.left.type === "app" &&
t.body.left.left.type === "app" &&
t.body.left.left.left.type === "app" &&
t.body.left.left.left.left.type === "idx" &&
t.body.left.left.left.left.idx === 0;
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