rework parsing; add support for parentheses.

README.md

@@ -91,7 +91,3 @@ here are the commands that are specific to this REPL:
 - `!.exit` exits the REPL.
 - `!.env` prints out all the named functions.
 - `!.clear` clears the console.
-
-## parentheses
-
-catgirl calculus supports using parentheses to group things. this implementation currently does not support this, thus it is non-compliant.

src/parse.mjs

@@ -1,6 +1,8 @@
 import Line from "./Line.mjs";
 import Expr from "./Expr.mjs";
 
+import { tokenize_line } from "./tokenize.mjs";
+
 const Invalid = "invalid";
 
 const Program = {
@@ -27,18 +29,6 @@ export function parse (code) {
 }
 
 export function parse_line (line) {
-	if (line.length === 0) {
-		return {
-			type: Line.Empty,
-		};
-	}
-
-	if (line[0] === "#") {
-		return {
-			type: Line.Comment,
-		};
-	}
-
 	if (line[0] === "!") {
 		return {
 			type: Line.Special,
@@ -46,7 +36,13 @@ export function parse_line (line) {
 		};
 	}
 
-	const tokens = line.split(/\s+/g).filter(t => t.length > 0);
+	const tokens = tokenize_line(line);
+
+	if (tokens.length === 0) {
+		return {
+			type: Line.Empty,
+		};
+	}
 
 	if (tokens.length >= 3 && tokens[1] === "=") {
 		return parse_binding(tokens);
@@ -67,8 +63,6 @@ function parse_binding (tokens) {
 
 	if (tokens.length < 3) return invalid();
 
-	// TODO: handle parentheses here.
-
 	const name = tokens[0];
 	if (!is_valid_name(name)) return invalid();
 
@@ -88,6 +82,7 @@ function parse_binding (tokens) {
 }
 
 function is_valid_name (name) {
+	if (typeof name !== "string") return false;
 	if (name.length === 0) return false;
 	if (name[0] === "#" || name[0] === "!") return false;
 	if (name === "=") return false;
@@ -114,16 +109,19 @@ function Token (value) {
 }
 
 function parse_expression (tokens) {
+	if (!Array.isArray(tokens)) {
+		return Token(tokens);
+	}
+	if (tokens.length === 1) {
+		return Token(tokens[0]);
+	}
+
 	if (tokens.length === 0) {
 		return {
 			type: Expr.Invalid,
 		};
 	}
 
-	if (tokens.length === 1) {
-		return Token(tokens[0]);
-	}
-
 	if (tokens.some(is_right_arrow)) {
 		return parse_function (tokens);
 	}
@@ -165,8 +163,8 @@ function parse_application (tokens) {
 	if (tokens.length === 2) {
 		return {
 			type: Expr.Application,
-			fn: Token(tokens[0]),
-			arg: Token(tokens[1]),
+			fn: parse_expression(tokens[0]),
+			arg: parse_expression(tokens[1]),
 		};
 	}
 

src/tokenize.mjs

@@ -0,0 +1,63 @@
+import Line from "./Line.mjs";
+
+
+
+export function tokenize_line (line) {
+	const tree = [];
+	const stack = [];
+	let node = tree;
+	let token = "";
+
+	function push (value) { node.push(value); }
+	function push_token () {
+		if (token.length > 0) {
+			push(token);
+			token = "";
+		}
+	}
+
+	const chars = line.split("");
+	for (const c of chars) {
+		if (is_parens_open(c)) {
+			push_token();
+
+			stack.push(node);
+			node.push([]);
+			node = node[node.length - 1];
+			continue;
+		}
+
+		if (is_parens_close(c)) {
+			push_token();
+			node = stack.pop();
+			continue;
+		}
+
+		if (is_whitespace(c)) {
+			push_token();
+			continue;
+		}
+
+		token += c;
+	}
+
+	push_token();
+	return tree;
+}
+
+function is_parens_open (c) {
+	return c === "(";
+}
+
+function is_parens_close (c) {
+	return c === ")";
+}
+
+function is_whitespace (c) {
+	return /\s/.test(c);
+}
+
+function exclude_comments (line) {
+	return line[0] !== "#";
+}
+