ashwin@uicsl.UUCP (05/08/84)
#R:boulder:-17500:uicsl:15500035:000:7288
uicsl!ashwin May 8 12:32:00 1984
<>
We use the LED editor which runs in InterLisp-VAX under UNIX. It's no DEDIT
but is better than the TTY editor. We have the source which should make it
pretty easy to set up on your system. I have no idea about copyright laws
etc., but I suppose I could mail it to you if you want it. Here's a write-up
on LED (from <LISPUSERS>LED.TTY):
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LED -- A display oriented extension to Interlisp's editor
-- for ordinary terminals.
LED is an add on to the standard Interlisp editor, which
maintains a context display continuously while editing. Other than
the automatically maintained display, the editor is unchanged except
for the addition of a few useful macros.
HOW TO USE
----------
load the file (see below)
possibly set screen control parameters to non-default values
edit normally
also: see documentation for SCREENOP to get LED to recognise your
terminal type.
THE DISPLAY
-----------
Each line of the context display represents a level of the list
structure you are editing, printed with PRINTLEVEL set to 0, 1, 2 or 3.
Highlighting is used to indicate the area on each line that is represented
on the line below, so you can thread your eye upward through successive
layers of code.
Normally, the top line of the screen displays the top level of the
edit chain, the second line displays the second level and so on. For
expressions deeper than LEDLINES levels, the top lines is the message:
(nnn more cars above)
and the next LEDLINES of the screen correspond to the BOTTOM levels
of the edit chain. When the edit chain does become longer than
LEDLINES, the display is truncated in steps of LEDLINES/2 lines, so
for example if LEDLINES=20 (the default) and your edit chain is 35
levels deep, the lisplay will be (20 more cars above) followed by
15 lines of context display representing the 20'th through 35'th
levels of the edit chain.
Each line, representing some level of the edit chain, is printed
such that it fits entirely on one screen line. Three methods are
used to accomplish the shortening of the printed representation:
Replacing comments with (*)
Setting PRINTLEVEL to a smaller value,
which changes expressions into ampersands
Truncting the leading and/or trailing expressions
around the attention point.
If the whole expression can't be printed, replacing comments is
tried first. If still to large, truncation is tried if the current
printlevel is >= LEDTLEV. Otherwise the whole process is restarted
with a smaller PRINTLEVEL.
The choice of LEDTLEV effectively chooses between seeing more detail
or seeing more forms.
The last line of the display, representing the "current" expression,
is printed onto ONE OR MORE lines of the display, controlled by the
variable LEDPPLINES and the amount of space (less than LEDLINES) available.
The line(s) representing the current expression are prettprinted with
elision, similar to the other context lines, using a prettyprint algorithm
similar to the standard prettyprinter. Default is LEDPPLINES=6, meaning
that up to six lines will be used to print the current expression. The
setting of LEDPPLINES can be manipulated from within the editor using
the (PPLINES n) command.
The rest of your screen, the part below the context display, is
available just as always to print into or do operations that do
not affect the edit chain (and therefor the appearance of the context
display). Each time the context display is updated, the rest of the
screen is cleared and the cursor positioned under the context display.
On terminals that have a "memory lock" feature to restrict the scrolling
region, it is used to protect the context display from scrolling
off the screen.
TERMINAL TYPES
--------------
Terminal types are currently supported:
HP2640 old HP terminals
HP26xx all other known HP terminals
Hazeltine 1520 hazeltine 1520 terminals
Heathkit sometimes known as Zenith
Ann Arbor Ambassador
The mapping between system terminal terminal type information and
internal types is via the alist SYSTEMTERMTYPES, which is used by
DISPLAYTERMP to set the variables CURRENTSCREEN and DISPLAYTERMTYPE.
Screen control macros: (in order of importance)
----------------------
DON turn on continuous display updating
DOF disable continuous display updating
CLR clear the display
CC clear the display and redo the context display
CT do a context display, incrementally updating the screen.
use CC and CT to get isolated displays even when automatic
updating is not enabled.
(LINES n) display at most n lines of context
default is 20
(PPLINES n) set the limit for prettyprinting the "current" expression.
(TRUNC n) allow truncation of the forms displayed if PLEV<=n
useful range is 0-3, default is 1
PB a one time "bracified" context display.
PL a one time context display with as much detail as possible.
pb and pl are varian display formats similar the the basic
context display.
Global variables:
-----------------
DISPON if T, continuous updating is on
DISPLAYTERMTYPE terminal type you are using. HP HP2640 of HZ
this is set automatically by (DISPLAYTERMTYPE)
HPENHANCECHAR enhancement character for HP terminals. A-H are possibilities.
LEDLINES maximum umber of lines of context to use. Default is 20.
LEDTLEV PLEV at which truncation becomes legal
LEDPPLINES maximum number of lines used to prettyprint the
current expression
FILES:
------
on TOPS-20 load <DDYER>LED.COM
on VAX/UNIX load LISPUSERS/LED.V
these others are pulled in automatically.
LED the list editor proper
SCREEN screen manipulation utilities.
PRINTOPT elision and printing utilities
SAMPLE DISPLAY
______________
(LAMBDA (OBJ DOIT LMARGIN CPOS WIDTH TOPLEV SQUEEZE OBJPOS) & & & & & @)
-12- NOTFIRST & CRPOS NEWWIDTH in OBJ do & & & & & @ finally & &)
(COND [& & &] (T & & &))
((LISTP I) (SETQ NEWLINESPRINTED &) [COND & &])
>> (COND ((IGREATERP NEWLINESPRINTED 0)
-2 2- (add LINESPRINTED NEWLINESPRINTED)
-2 3- (SETQ NEWLINE T))
-3- (T (add POS (IMINUS NEWLINESPRINTED))
-3 3- (COND (SQUEEZE &))))
Except that you can't really see the highlighted forms, this is a
representative LED context display. In an actual display, the @s
would be highlighted &s, and the [bracketed] forms would be highlighted.
The top line represents the whole function being edited. Because the
CADR is a list of bindings, LED prefers to expand it if possible so you
can see the names.
The second line is a representation of the last form in the function, which
is highlighted on the first line. The -12- indicates that there are 12
other objects (not seen) to the left. The @ before "finally" marks where
the edit chain descends to the line below.
The third and fourth lines descend through the COND clause, to an imbedded
COND cluase which is the "current expression"
The current expression is marked by ">>" at the left margin, and an
abbreviated representation of it is printed on the 5'th through 9'th
lines. The expressions like "-2 3-" at the left of the prettyprinted
representation are the edit commands to position at that form.
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...uiucdcs!uicsl!ashwin