TeXmacs trees

All TeXmacs documents or document fragments can be thought of as trees. For instance, the tree

typically represents the formula

Internal nodes of TeXmacs trees

Each of the internal nodes of a TeXmacs tree is a string symbol and each of the leafs is an ordinary string. A string symbol is different from a usual string only from the efficiency point of view: TeXmacs represents each symbol by a unique number, so that it is extremely fast to test weather two symbols are equal.

Leafs of TeXmacs trees

Currently, all strings are represented using the universal TeXmacs encoding. This encoding coincides with the Cork font encoding for all characters except “<” and “>”. Character sequences starting with “<” and ending with “>” are interpreted as special extension characters. For example, <alpha> stands for the letter α. The semantics of characters in the universal TeXmacs encoding does not depend on the context (currently, cyrillic characters are an exception, but this should change soon). In other words, the universal TeXmacs encoding may be seen as an analogue of Unicode. In the future, we might actually switch to Unicode.

The string leafs either contain ordinary text or special data. TeXmacs supports the following atomic data types:

Boolean numbers

Either true or false.

Integers

Sequences of digits which may be preceded by a minus sign.

Floating point numbers

Specified using the usual scientific notation.

Lengths

Floating point numbers followed by a length unit, like 29.7cm or 2fn.

Serialization and preferred syntax for editing

When storing a document as a file on your harddisk or when copying a document fragment to the clipboard, TeXmacs trees have to be represented as strings. The conversion without loss of information of abstract TeXmacs trees into strings is called serialization and the inverse process parsing. TeXmacs provides three ways to serialize trees, which correspond to the standard TeXmacs format, the XML format and the Scheme format.

However, it should be emphasized that the preferred syntax for modifying TeXmacs documents is the screen display inside the editor. If that seems surprising to you, consider that a syntax is a way to represent information in a form suitable to understanding and modification. The on-screen typeset representation of a document, together with its interactive behaviour, is a particularly concrete syntax. Moreover, in the Document→View menu, you may find different ways to customize the way documents are viewed, such as different levels of informative flags and a “source tree” mode for editing style files.