Learning GNU Emacs, 3rd Edition

Writing Code

We have already seen various examples of Emacs modes, including text mode (see Chapter 2) and shell mode (see Chapter 5). Special functionality like the buffer list (see Chapter 4) and Dired (see Chapter 5) are actually modes as well. All modes have two basic components: an Emacs Lisp package that implements the mode and a function that invokes it.

Language Modes

The version of Emacs on which this book is based (21.3.5) comes with language modes for Ada, assembly, awk, C, C++, Common Lisp, Fortran, ICON, Java, Lisp, MIM, Modula-2, Objective-C, Pascal, Pike, Perl, PROLOG, Python, Scheme, SGML, Simula, and SQL; future versions will undoubtedly add more. Many—but not all—of the language modes are "hooked" into Emacs so that if you visit a file with the proper filename suffix, you will automatically be put in the correct mode. To find out whether Emacs does this for the language you use, look up your language in the table of Emacs Lisp packages in Appendix B. If one or more suffixes is listed in the right-hand column, Emacs invokes the mode for files with those suffixes.

However, if no suffix is listed (or if your compiler supports a different suffix than the ones listed), you can set up Emacs to invoke the mode automatically when you visit your source files. You need to do two things: first, look again at the right-hand column in the package table entry for your language, and you will find the name of the function that invokes the mode (e.g., ada-mode, modula-2-mode ...