@Section
   @Title { Errors }
   @Tag { grerrors }
@Begin
@PP
Lout normally produces an output file that will print without mishap on
any PostScript device.  However, some of the options of @Code "@Graph"
and all of the data and labels are passed through Lout to the output
file without checking.  Any errors in this material will not be detected
until the file is printed.
@PP
The most likely errors are {@I rangecheck @I errors}, for example if
an attempt is made to divide by zero or take the square root of a
negative number, and {@I undefined @I errors}, arising from symbols
misspelt, use of @Code "x" outside an {@Code "xloop"}, etc.  Less commonly,
everything may be correct but the graph is too large in some
way:  too much data, expression too deeply nested, etc.  All the data
is stored in the printer while the graph is being printed, after which
the data is discarded and all memory consumed by the graph is reclaimed.
@PP
When an error is detected, @Code "@Graph" arranges for the offending page
to be printed up to the point where the error occurred, with a message
nearby describing the error.  Printing of the document is then
aborted.  The problem is usually easy to locate since it lies in whatever
should have been printed next.
@PP
Older versions of the popular GhostView previewer have a bug which causes
exponents in labels to be printed in diminishing sizes.  Recent versions
no longer have this problem.
@End @Section
