edit --Command, zero or one input. Abbreviation: ed
     The input to this command must be a word, which is the name of a
     procedure, or a list of words, each of which is the name of a
     procedure. (Unlike the to command, but like all other Logo
     procedures, the edit command evaluates its input, so you must use a
     quotation mark before the procedure name, if only one is given, to
     indicate that it is the name itself which is the input to edit;
     otherwise Logo would actually run the procedure to calculate the input
     to edit.) The procedure you name may or may not already be defined.
     Logo responds to the edit command by running the text editor edt,
     editing the definition of the procedure(s) named in its input. (If a
     procedure was not previously defined, Logo creates an initial
     definition for it which contains only a title line and the end line.)
     You then edit the definition(s) with edt. When you write the file and
     leave edt, Logo will use the edited file as the definition(s) of the
     procedure(s). You must not put anything in the file except procedure
     definitions; in other words, every nonempty line in the file must be
     between a "to" line and an "end" line.

     If the edit command is given with no input, edt is given the same file
     as from the last time you used the edit command. This is a
     convenience for editing the same procedure(s) repeatedly.

     If, while editing, you change your mind and want to leave edt without
     redefining anything, use the command ESC ^Z instead of the normal ^Z.
     This special way of leaving edt tells Logo not to redefine your
     procedures. You have the choice, before exiting edt, of writing or
     not writing the temporary file which contains the definitions. If you
     don't write the file, another edit command with no input will re-read
     the previous contents of the temporary file; if you do, another edit
     will re-read the new version.

     If your Unix environment contains a variable named EDITOR, the
     contents of that variable is used as the name of the text editor
     program instead of the standard edt. The variable can contain a full
     pathname, or just a program name if the program can be found in /bin
     or /usr/bin. Your favorite editor may not have a facility like edt's
     ESC ^Z to abort redefinition.