[ Thanks to Diego
Restrepo for this link. ]
“GNU TeXmacs is a free, scientific text editor, which was
inspired by both TeX and GNU Emacs. The editor allows you to write
structured documents via a user-friendly, WYSIWYG
(what-you-see-is-what-you-get) interface.“New document styles may be created by the user. The program
implements high-quality typesetting algorithms incorporating TeX
fonts, which helps you to produce professional looking
documents.“Automatically generated formulas retain high-quality
typsetting, which makes TeXmacs suitable as an interface for CAS
(computer algebra systems). TeXmacs also supports the Guile/Scheme
extension language, so that you may customize the interface and
write your own extensions to the editor…