Editing GNU TeXmacs (section)

==The TeXmacs format==

All TeXmacs documents or document fragments can be thought of as trees (the concept of tree exists as well in the [[Standard Generalized Markup Language|SGML]] markup language, to which the Texmacs format is similar). For instance, the tree

[[File:TeXmacs tree.png| 300px]]

represents the formula

:<math>x+y+\frac{1}{2}+\sqrt{y+z}</math>

(written here with the TeX markup used by Wikipedia) and is turned by TeXmacs' own typesetting engine into a typeset formula, here inserted as an image:

:[[File:TeXmacs tree rendered.png|158x158px]]

TeXmacs trees are represented in TeXmacs files as strings, and in the TeXmacs editor as the typeset representation of the document together with its interactive behaviour.<ref>{{Cite web|url=https://www.texmacs.org/tmweb/manual/webman-format.en.html|title=The TeXmacs format|last=van der Hoeven|first=Joris|access-date=2019-08-10}}</ref> In the on-screen representation of the TeXmacs tree, the cursor movement represents the movement inside the tree. On disk, three representations of the TeXmacs format exist: a native representation, an XML representation and a representation with Scheme S-expressions; the Scheme representation is useful for the interfacing with Scheme programs.