From: Jim Pryor <profjim@jimpryor.net>
Date: Thu, 23 Sep 2010 08:46:54 +0000 (-0400)
Subject: tweak lambda evaluator
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=a3b99e629ce7473014b705dbb8ea9c4321639805

tweak lambda evaluator

Signed-off-by: Jim Pryor <profjim@jimpryor.net>
---

diff --git a/code/parse.js b/code/parse.js
index 8a4761b5..382ba029 100644
--- a/code/parse.js
+++ b/code/parse.js
@@ -126,13 +126,8 @@ var make_parse = function () {
         return body;
     };
 
-    var number_handler = function () {
-
-    };
-
     symbol("(end)");
     symbol("(name)").handler = name_handler;
-    symbol("(number)").handler = number_handler;
     symbol("let").handler = lambda_handler;
     symbol("=").handler = branch_handler;
     symbol("in");
@@ -144,23 +139,6 @@ var make_parse = function () {
 
 	function make_constants() {
 
-		var constant = function (s, v) {
-			var x = symbol(s);
-			x.handler = function () {
-				this.value = symbol_table[this.id].value;
-				if (this.first) {
-					return make_app(this.first.handler(), this.value);
-				} else {
-					return this.value;
-				}
-			};
-			// constants have their own id and arity = literal
-			// numbers have id = "(number)" and arity = literal
-			x.arity = "literal";
-			x.value = v;
-			return x;
-		};
-
 		function make_lam2(a, b, aa) {
 			return make_lam(a, make_lam(b, aa));
 		}
@@ -182,6 +160,39 @@ var make_parse = function () {
 		var zz = new Lambda_var(z);
 		var_table = { u: u, v: v, x: x, s: s, z: z};
 		name_table = {u: uu, v: vv, x: xx, s: ss, z: zz};
+		number_table = {};
+
+		// constants have their own id and arity = literal
+		// numbers have id = "(number)" and arity = literal
+		symbol("(number)").handler = function () {
+			var n = this.value;
+			var res = number_table[n];
+			if (!res) {
+				res = zz;
+				while (n > 0) {
+					n -= 1;
+					res = make_app(ss, res);
+				}
+				res = make_lam2(s, z, res);
+				number_table[this.value] = res;
+			}
+			return res;
+		}
+
+		var constant = function (s, v) {
+			var x = symbol(s);
+			x.handler = function () {
+				this.value = symbol_table[this.id].value;
+				if (this.first) {
+					return make_app(this.first.handler(), this.value);
+				} else {
+					return this.value;
+				}
+			};
+			x.arity = "literal";
+			x.value = v;
+			return x;
+		};
 
 		constant("S", make_lam3(u, v, x, make_app3(uu, xx, make_app(vv, xx))));
 		constant("K", make_lam2(u, v, uu));
@@ -190,6 +201,7 @@ var make_parse = function () {
 		constant("C", make_lam3(u, v, x, make_app3(uu, xx, vv)));
 		constant("W", make_lam2(u, v, make_app3(uu, vv, vv)));
 		constant("T", make_lam2(u, v, make_app(vv, uu)));
+
 	}
 	make_constants();