32 Text

This chapter describes the functions that deal with the text in a buffer. Most examine, insert, or delete text in the current buffer, often operating at point or on text adjacent to point. Many are interactive. All the functions that change the text provide for undoing the changes (see Undo).

Many text-related functions operate on a region of text defined by two buffer positions passed in arguments named start and end. These arguments should be either markers (see Markers) or numeric character positions (see Positions). The order of these arguments does not matter; it is all right for start to be the end of the region and end the beginning. For example, (delete-region 1 10) and (delete-region 10 1) are equivalent. An args-out-of-range error is signaled if either start or end is outside the accessible portion of the buffer. In an interactive call, point and the mark are used for these arguments.

Throughout this chapter, “text" refers to the characters in the buffer, together with their properties (when relevant). Keep in mind that point is always between two characters, and the cursor appears on the character after point.

• Near Point		Examining text in the vicinity of point.
• Buffer Contents		Examining text in a general fashion.
• Comparing Text		Comparing substrings of buffers.
• Insertion		Adding new text to a buffer.
• Commands for Insertion		User-level commands to insert text.
• Deletion		Removing text from a buffer.
• User-Level Deletion		User-level commands to delete text.
• The Kill Ring		Where removed text sometimes is saved for later use.
• Undo		Undoing changes to the text of a buffer.
• Maintaining Undo		How to enable and disable undo information. How to control how much information is kept.
• Filling		Functions for explicit filling.
• Margins		How to specify margins for filling commands.
• Adaptive Fill		Adaptive Fill mode chooses a fill prefix from context.
• Auto Filling		How auto-fill mode is implemented to break lines.
• Sorting		Functions for sorting parts of the buffer.
• Columns		Computing horizontal positions, and using them.
• Indentation		Functions to insert or adjust indentation.
• Case Changes		Case conversion of parts of the buffer.
• Text Properties		Assigning Lisp property lists to text characters.
• Substitution		Replacing a given character wherever it appears.
• Registers		How registers are implemented. Accessing the text or position stored in a register.
• Transposition		Swapping two portions of a buffer.
• Replacing		Replacing the text of one buffer with the text of another buffer.
• Decompression		Dealing with compressed data.
• Base 64		Conversion to or from base 64 encoding.
• Checksum/Hash		Computing cryptographic hashes.
• GnuTLS Cryptography		Cryptographic algorithms imported from GnuTLS.
• Parsing HTML/XML		Parsing HTML and XML.
• Parsing JSON		Parsing and generating JSON values.
• JSONRPC		JSON Remote Procedure Call protocol
• Atomic Changes		Installing several buffer changes atomically.
• Change Hooks		Supplying functions to be run when text is changed.