X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=code%2Fparse.js;h=8856b164aa86b96acf69000016995b3f039779fe;hp=cb412f7fe523c3d0b7ab1fd98876c14fa11a8955;hb=934f19eef90e5474be0af07e7400867538068bc9;hpb=df6a6fe6807edabf1b3c3e904eb2ead20eedf0ca

diff --git a/code/parse.js b/code/parse.js
index cb412f7f..8856b164 100644
--- a/code/parse.js
+++ b/code/parse.js
@@ -4,6 +4,9 @@
 //      http://javascript.crockford.com/tdop/index.html
 //      Douglas Crockford 2010-06-26
 
+//      See also http://effbot.org/zone/simple-top-down-parsing.htm
+
+
 /*jslint onevar: false
  */
 
@@ -34,14 +37,14 @@ var make_parse = function () {
         a = t.type;
         if (a === "name") {
             o = symbol_table[v];
-            if (o && typeof o !== 'function') {
-                a = "keyword";
-            } else {
+            if (!o || typeof o === 'function') {
                 o = symbol_table["(name)"];
+            } else {
+                a = o.arity || "keyword";
             }
         } else if (a ===  "number") {
-            o = symbol_table["(literal)"];
-            a = "literal";
+            o = symbol_table["(number)"];
+			a = "literal";
         } else if (a === "operator") {
             o = symbol_table[v];
             if (!o) {
@@ -65,6 +68,7 @@ var make_parse = function () {
         }
     };
 
+	/*
 	try {
 		if (console && console.debug) {
 			function print() {
@@ -72,6 +76,7 @@ var make_parse = function () {
 			}
 		}
 	} catch (e) {}
+	*/
 
     var symbol = function (id) {
         var s = symbol_table[id];
@@ -79,7 +84,6 @@ var make_parse = function () {
             s = Object.create(original_symbol);
             s.id = s.value = id;
             symbol_table[id] = s;
-			print(s, s.arity);
         }
         return s;
     };
@@ -127,14 +131,8 @@ var make_parse = function () {
         return body;
     };
 
-
-    var itself = function () {
-        return this;
-    };
-
     symbol("(end)");
     symbol("(name)").handler = name_handler;
-    symbol("(literal)").handler = itself;
     symbol("let").handler = lambda_handler;
     symbol("=").handler = branch_handler;
     symbol("in");
@@ -146,17 +144,6 @@ 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;
-				this.arity = "literal";
-				return this;
-			};
-			x.value = v;
-			return x;
-		};
-
 		function make_lam2(a, b, aa) {
 			return make_lam(a, make_lam(b, aa));
 		}
@@ -178,6 +165,43 @@ 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;
+			}
+			if (this.first) {
+				return make_app(this.first.handler(), res);
+			} else {
+				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));
@@ -186,6 +210,7 @@ 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();
 
@@ -208,12 +233,16 @@ var make_parse = function () {
                 return t;
             } else {
                 t.first = [];
-                while (token.arity === "name") {
-                    t.first.push(n);
-                    n = token;
+                while (token.arity === "name" || token.id === "\\") {
+                      t.first.push(n);
+                      n = token;
                     advance();
                 }
-                if (token.id === ".") {
+				if (token.arity === "literal" && t.first.length === 0) {
+					t.first.push(n);
+					t.second = token;
+					advance();
+				} else if (token.id === ".") {
                     t.first.push(n);
                     advance();
                     t.second = expression(in_let);
@@ -249,8 +278,8 @@ var make_parse = function () {
                     n = token;
                     advance(")");
                 } else {
-                    if (token.arity !== "name") {
-                        token.error("Expected a variable name.");
+                    if (token.arity !== "name" && token.arity !== "literal") {
+                        token.error("Expected a variable name or literal.");
                     }
                     token.first = n;
                     n = token;