Next: Trace Buffer, Previous: Eval List, Up: Edebug [Contents][Index]
If an expression in your program produces a value containing circular list structure, you may get an error when Edebug attempts to print it.
One way to cope with circular structure is to set print-length
or print-level to truncate the printing. Edebug does this for
you; it binds print-length and print-level to the values
of the variables edebug-print-length and
edebug-print-level (so long as they have non-nil
values). See Output Variables.
If non-nil, Edebug binds print-length to this value while
printing results. The default value is 50.
If non-nil, Edebug binds print-level to this value while
printing results. The default value is 50.
You can also print circular structures and structures that share
elements more informatively by binding print-circle
to a non-nil value.
Here is an example of code that creates a circular structure:
(setq a '(x y)) (setcar a a)
Custom printing prints this as ‘Result: #1=(#1# y)’. The ‘#1=’ notation labels the structure that follows it with the label ‘1’, and the ‘#1#’ notation references the previously labeled structure. This notation is used for any shared elements of lists or vectors.
If non-nil, Edebug binds print-circle to this value while
printing results. The default value is t.
Other programs can also use custom printing; see cust-print.el for details.