move function

util/pretty.js

@@ -1,5 +1,38 @@
 import { inspect } from 'node:util';
+import { symbolFunction, symbolList, symbolProduct, symbolSum } from '../structures/types.js';
 
 export function pretty(obj) {
   return inspect(obj, { colors: true, depth: null, breakLength: 120 });
 }
+
+// Pretty print type
+export function prettyT(type) {
+  // console.log("pretty:", type);
+  if (typeof type === "symbol") {
+    return type.description;
+  }
+  if (type.typeVars) {
+    if (type.typeVars.size > 0) {
+      return `∀${[...type.typeVars].map(prettyT).sort((a, b) => a.localeCompare(b)).join(",")}: ${prettyT(type.type)}`;
+    }
+    else {
+      return prettyT(type.type);
+    }
+  }
+  if (type.symbol === symbolFunction) {
+    return `(${prettyT(type.params[0])} -> ${prettyT(type.params[1])})`;
+  }
+  if (type.symbol === symbolList) {
+    return `[${prettyT(type.params[0])}]`;
+  }
+  if (type.symbol === symbolProduct) {
+    return `(${prettyT(type.params[0])} × ${prettyT(type.params[1])})`;
+  }
+  if (type.symbol === symbolSum) {
+    return `(${prettyT(type.params[0])} | ${prettyT(type.params[1])})`;
+  }
+  if (type.params.length === 0) {
+    return type.symbol.description;
+  }
+  return `${type.symbol.description}(${type.params.map(prettyT).join(", ")})`;
+}