Chapter 9. Computer Language Support

As many programmers know, the task of programming usually breaks down into a cycle of think-write-debug. If you have used Unix (or various other operating systems) for programming, you have probably become accustomed to using separate tools for each phase of the cycle, for example, a text editor for writing, a compiler for compiling, and the operating system itself for running programs. You would undoubtedly find an environment much more productive if the boundaries between the cycle phases and the tools that support them were erased.

Emacs provides considerable support for writing, running, and debugging programs written in a wide variety of languages, and it integrates this support into a smooth framework. You never have to leave Emacs when developing programs, so you will find it easier to concentrate on the actual programming task (i.e., the "think" part of the cycle) because you won't have to spend lots of time going from one tool to another.

When you write code, you can use one of Emacs's programming language modes; these turn Emacs into a spiffy syntax-directed or language-sensitive editor that knows about the syntax of the language. That makes it easier for you to write code in a uniform, easy-to-read, customizable style. Language modes exist for several different programming languages.

Emacs also supports running and debugging programs. Shell mode (see Chapter 5) and multiple windows (see Chapter 4) allow you to run your code while editing it. Emacs has a powerful facility for interfacing to many compilers and the Unix make command: Emacs can interpret compilers' error messages and visit files where errors occur at the appropriate line number. Indeed, many tools (such as the Java build tool, ant) include command-line options to format their output in an Emacs-friendly way.

In this chapter, we cover the features of language modes in general such as compiling and debugging programs, comments, indentation, and syntax highlighting. We also spend a bit of time upfront looking at the etags facility, which is a great help to programmers who work on large, multifile projects. These features apply to all language modes. We then delve into Emacs's support for various languages, including C, C++, Java, Perl, SQL, and Lisp.