lex & yacc, 2nd Edition

Chapter 4. A Menu Generation Language

The previous chapter provided a simple example of an interpreter, a desktop calculator. In this chapter, we turn our attention to compiler design by developing a menu generation language (MGL) and its associated compiler. We begin with a description of the language that we are going to create. Then we look at several iterations of developing the lex and yacc specifications. Lastly, we create the actions associated with our grammar and which implement the features of the MGL.

Overview of the MGL

We’ll develop a language that can be used to generate custom menu interfaces. It will take as input a description file and produce a C program that can be compiled to create this output on a user’s terminal, using the standard curses library to draw the menus on the screen.^[11]

In many cases when an application requires a lot of tedious and repetitive code, it is faster and easier to design a special purpose language and write a little compiler that translates your language into C or something else your computer can already handle. Curses programming is tedious, because you have to position all of the data on the screen yourself. MGL automates most of the layout, greatly easing the job.

The menu description consists of the following:

1. A name for the menu screen

2. A title or titles

3. A list of menu items, each consisting of:

   item

   [ command ]

   action

   [ attribute ]

   where item is the text string that appears on the menu, command is the mnemonic used to provide command-line ...