--- /dev/null
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file holds the go generate command to run yacc on the grammar in expr.y.
+// To build expr:
+// % go generate
+// % go build
+
+//go:generate goyacc -o expr.go -p "expr" expr.y
+
+// Expr is a simple expression evaluator that serves as a working example of
+// how to use Go's yacc implementation.
+package main