lefty [ options ] [ file ]
lefty is a two-view graphics editor for technical pictures. This editor
has no hardwired knowledge about specific picture layouts or editing
operations. Each picture is described by a program that contains func-
tions to draw the picture and functions to perform editing operations
that are appropriate for the specific picture. Primitive user actions,
like mouse and keyboard events, are also bound to functions in this
program. Besides the graphical view of the picture itself, the editor
presents a textual view of the program that describes the picture. Pro-
grammability and the two-view interface allow the editor to handle a
variety of pictures, but are particularly useful for pictures used in
technical contexts, e.g., graphs and trees. Also, lefty can communicate
with other processes. This feature allows it to use existing tools to
compute specific picture layouts and allows external processes to use
the editor as a front end to display their data structures graphically.
The file name is optional. It may be -, for reading from standard
input. lefty uses two environment variables, LEFTYPATH and LEFTYOP-
TIONS. LEFTYPATH is a colon separated list of directories. When lefty
tries to open a file, it searches that path for the file. When lefty
tries to start up another process, it searches LEFTYPATH first, then
the standard PATH variable. LEFTYOPTIONS can be used to set specific
options. Options specified on the command line override options set
through this variable.
-x Instructs the editor to exit after processing file.
<expression> is parsed and executed.
Set error reporting level. The default value is 0. 0 never
prints any messages. 1 prints severe errors, such as trying to
return from a non function. 2 is the most useful: it reports
function calls that cannot be executed, either because there is
no function, or because of argument mismatches. 3 also warns
about bad variable names. 4,5 warn about expressions that do
not return a value. Only level 1 messages are real errors. The
rest arise from legal lefty statements, but may be caused by
some logic errors.
Specifies how much of the stack to show, when an error message
is to be printed. The default value is 2. With 0, no part of
the stack is shown. With 1, only the top stack frame is printed.
With 2, the full stack is printed.
Specifies a default file name for postscript files. This name is
used when no name is specified in the createwidget call. The
default file name is out.ps.
-V Prints the version.
lefty user guide.
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