TECO.EL

TECO was an ancient text editor written in the days before most of you reading this were born. It supported macros of editing commands as an extension mechanism. The original version of EMACS was written by loading macros into TECO that provided EMACS functionality and then saving the memory image of the combined TECO command interpreter and the macros as a new program ("dumping an EMACS").

As an editor, the TECO commands (the operators of the macro language) were terse and powerful. Within TECO-based EMACS, one could open a 'minibuffer' by typing ESC ESC and then enter a TECO program which would be run (by typing ESC ESC again) to modify the underlying EMACS buffer. E.g. if you wanted to add a new column containing the string 'EMPTY' between the second and third columns of a CSV file, you could execute the TECO program

<.-z; 2fwl i,EMPTY$ l>

"<" loop body ">"
".-z" - an integer expression: current point - end of buffer
";" - end loop test, if prefix arg ".-z" is >= 0, you exit the loop
"2fwl" - really three things: "2" => repeat count, "fw" => bounds of a word, and "l" => move forward using prefix arg bounds
"iSTRING-TO-INSERT$" (where $ is actually ESC)
"l" - with no args, move to the beginning of the next line

While this is easily done in modern ELisp-based EMACS with a keyboard macro, the TECO language offers more functionality than keyboard macros and is often quicker to use. Personally, I'm addicted to clearing a buffer by executing the short TECO program hk.

Dale Worley (worley@alum.mit.edu) implemented this TECO interpreter in Elisp. It was originally available from the old EMACS LCD archive and is still kicking around the EmacsWiki. I created this package to make it available from the modern Emacs package system.