21 Editing Programs

SXEmacs provides specialized support for editing source files for many different programming languages. For example it is possible to

• Follow the usual indentation conventions of the language (see Grinding).
• Move over or kill balanced expressions or sexps (see Lists).
• Move over or mark top-level balanced expressions (defuns, in Lisp; functions, in C).
• Show how parentheses balance (see Matching).
• Insert, kill, or align comments (see Comments).
• Find functions and symbols in program by name (see Tags).

The commands available for words, sentences, and paragraphs are useful in editing code even though their canonical application is for editing human language text. Most symbols contain words (see Words); sentences can be found in strings and comments (see Sentences). Paragraphs per se are not present in code, but the paragraph commands are useful anyway, because Lisp mode and C mode define paragraphs to begin and end at blank lines (see Paragraphs). Judicious use of blank lines to make the program clearer also provides interesting chunks of text for the paragraph commands to work on.

The selective display feature is useful for looking at the overall structure of a function (see Selective Display). This feature causes only the lines that are indented less than a specified amount to appear on the screen.