add special renderer for church booleans.

src/renderers/church_boolean.mjs

@@ -0,0 +1,16 @@
+import { is_same } from "../serialize.mjs";
+
+const T = [0, [0, 2]];
+const F = [0, [0, 1]];
+
+export default {
+	check: expr => {
+		if (is_same(expr, T)) return true;
+		if (is_same(expr, F)) return true;
+		return false;
+	},
+	render: (expr, prettify) => {
+		if (is_same(expr, T)) return "true";
+		if (is_same(expr, F)) return "false";
+	},
+};

src/renderers/main.mjs

@@ -0,0 +1,4 @@
+import { add_special_renderer } from "../prettify.mjs";
+import church_boolean from "./church_boolean.mjs";
+
+add_special_renderer(church_boolean);

src/repl.mjs

@@ -7,6 +7,7 @@ import { transpile } from "./transpile.mjs";
 import { reduce } from "./reduce.mjs";
 
 import { prettify } from "./prettify.mjs";
+import "./renderers/main.mjs";
 
 import readline from "node:readline";
 

src/serialize.mjs

@@ -3,3 +3,7 @@ export function serialize (expr) {
 		? "(" + expr.map(serialize).join(",") + ")"
 		: expr;
 }
+
+export function is_same (a, b) {
+	return serialize(a) === serialize(b);
+}