parse productions

dhconnelly · Dec 6, 2012 · a7678d7 · a7678d7
1 parent e416cd7
commit a7678d7
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diff --git a/prettybnf.js b/prettybnf.js
@@ -121,4 +121,15 @@ Parser.prototype.expressions = function () {
     return { type: 'expressions', expressions: expressions };
 };
 
+// <production> ::= <nonterminal> <ws> "::=" <ws> <expressions> ";";
+Parser.prototype.production = function () {
+    var lhs = this.nonterminal();
+    this.ws();
+    this.eat(':'); this.eat(':'); this.eat('=');
+    this.ws();
+    var rhs = this.expressions();
+    this.eat(';');
+    return { type: 'production', lhs: lhs, rhs: rhs };
+};
+
 }(typeof exports === 'undefined' ? this.prettybnf = {} : exports));
diff --git a/test_prettybnf.js b/test_prettybnf.js
@@ -121,3 +121,17 @@ exports.testParser_expressions = function (t) {
     t.throws(function () { new Parser('| <a>').expressions(); }, SyntaxError);
     t.done();
 };
+
+exports.testParser_production = function (t) {
+    var node = new Parser('<a>\t::=   <b> | "c" <d> | ""\n\t;').production();
+    t.equal(node.type, 'production');
+    t.equal(node.lhs.type, 'nonterminal');
+    t.equal(node.rhs.type, 'expressions');
+    t.equal(node.rhs.expressions.length, 3);
+    t.throws(function () { new Parser(' <a> ::= "b";').production(); }, SyntaxError);
+    t.throws(function () { new Parser('::= "b";').production(); }, SyntaxError);
+    t.throws(function () { new Parser('<a> ::= ;').production(); }, SyntaxError);
+    t.throws(function () { new Parser('<a> ').production(); }, SyntaxError);
+    t.throws(function () { new Parser('<a> ::= "b"').production(); }, SyntaxError);
+    t.done();
+};