Initial JS runtime and Arborix Implementation

2026-05-06 11:30:31 -05:00
parent fe453b9b96
commit 0cd849447f
24 changed files with 1865 additions and 104 deletions
--- a/ext/js/src/codecs.js
+++ b/ext/js/src/codecs.js
@@ -0,0 +1,135 @@
+/**
+ * codecs.js — Minimal codecs for decoding tree results.
+ *
+ * Implements: decodeResult (from Research.hs)
+ *   - Leaf → "t"
+ *   - Numbers: toNumber
+ *   - Strings: toString
+ *   - Lists: toList
+ *   - Fallback: raw tree format
+ */
+
+// ── toNumber ────────────────────────────────────────────────────────────────
+
+/**
+ * Decode a tree as a binary number (big-endian).
+ * Leaf = 0, Fork(Leaf, rest) = 2*n, Fork(Stem Leaf, rest) = 2*n+1.
+ */
+export function toNumber(t) {
+  if (!Array.isArray(t)) return null;
+  if (t.length === 0) return 0; // Leaf = 0
+  if (t.length !== 2) return null; // must be Fork
+
+  const [right, left] = t;
+  // Fork structure: [right, left]
+  // left child determines bit: Leaf = 0, Stem(Leaf) = 1
+  let bit;
+  if (Array.isArray(left) && left.length === 0) {
+    bit = 0; // Leaf
+  } else if (Array.isArray(left) && left.length === 1) {
+    const child = left[0];
+    if (Array.isArray(child) && child.length === 0) {
+      bit = 1; // Stem(Leaf) = 1
+    } else {
+      return null; // Stem of something other than Leaf
+    }
+  } else {
+    return null;
+  }
+
+  const rest = toNumber(right);
+  if (rest === null) return null;
+
+  return bit + 2 * rest;
+}
+
+// ── toString ────────────────────────────────────────────────────────────────
+
+/**
+ * Decode a tree as a list of numbers (characters).
+ * Fork(x, rest) = x : list.
+ */
+export function toList(t) {
+  if (!Array.isArray(t)) return null;
+  if (t.length === 0) return []; // Leaf = empty list
+  if (t.length !== 2) return null; // must be Fork
+
+  const [right, left] = t;
+  const rest = toList(right);
+  if (rest === null) return null;
+
+  return [left, ...rest];
+}
+
+/**
+ * Decode a tree as a string.
+ */
+export function toString(t) {
+  const list = toList(t);
+  if (list === null) return null;
+  try {
+    return list.map((ch) => String.fromCharCode(ch)).join("");
+  } catch {
+    return null;
+  }
+}
+
+// ── decodeResult ────────────────────────────────────────────────────────────
+
+/**
+ * Decode a tree result using multiple strategies:
+ *   1. Leaf → "t"
+ *   2. String (if all chars are printable)
+ *   3. Number
+ *   4. List
+ *   5. Raw tree format
+ */
+export function decodeResult(t) {
+  if (!Array.isArray(t)) {
+    return String(t);
+  }
+
+  // Leaf
+  if (t.length === 0) {
+    return "t";
+  }
+
+  // Try string first (list of char codes)
+  const list = toList(t);
+  if (list !== null && list.length > 0) {
+    const str = list.map((n) => {
+      if (n < 32 || n > 126) return null;
+      return String.fromCharCode(n);
+    }).join("");
+    if (str) return `"${str}"`;
+  }
+
+  // Try number
+  const num = toNumber(t);
+  if (num !== null) {
+    return String(num);
+  }
+
+  // Try list (elements are trees)
+  if (t.length === 2) {
+    const elements = toList(t);
+    if (elements !== null) {
+      const decoded = elements.map((e) => decodeResult(e));
+      return `[${decoded.join(", ")}]`;
+    }
+  }
+
+  // Raw tree format
+  return formatTree(t);
+}
+
+/**
+ * Format a tree as a parenthesized expression.
+ */
+export function formatTree(t) {
+  if (!Array.isArray(t)) return String(t);
+  if (t.length === 0) return "Leaf";
+  if (t.length === 1) return `Stem(${formatTree(t[0])})`;
+  if (t.length === 2) return `Fork(${formatTree(t[1])}, ${formatTree(t[0])})`;
+  return `[${t.map(formatTree).join(", ")}]`;
+}