Trivial Toplevel Prompt

Trivial Toplevel Prompt is a petty portability library to set the implementation-specific REPL prompt to a new, possibly more useful, value. It allows showing the inspect/debug/stepping statuses alongside the command number, current package, and current process or thread.

Tested on SBCL, CCL, ECL, ABCL, CLISP, Allegro CL (basically all the implementations I can run), and CMUCL (untested, incomplete). Help in supporting other implementations (like LispWorks with its *prompt*) is much appreciated!

Getting started

Clone the Git repository:

git clone https://github.com/aartaka/trivial-toplevel-prompt ~/common-lisp/

And then load :trivial-toplevel-prompt in the REPL:

(asdf:load-system :trivial-toplevel-prompt)
;; or, if you use Quicklisp
(ql:quickload :trivial-toplevel-prompt)

You can also install Trivial Toplevel Prompt via Guix, using the bundled guix.scm file:

guix package -f guix.scm

APIs

The main API function is set-toplevel-prompt. The values that it accepts are:

String

use it as a format control.

Function

use it to print the prompt to the REPL stream.

Arguments provided to both the format control and the printing function are (mostly modeled after Allegro CL APIs):

• Stream to print the prompt to. Only provided for the function, implied for the string.
• The current process/thread name (a string) or NIL when not provided/meaningless.
• The shortest possible name/nickname of the current package (cl:*package*).
• A number indicating the command/expression number.
• A number indicating the current break/debug level.
• A boolean indicating whether stepping is enabled.
• A boolean indicating whether inspect is in progress.

Note that some implementations have custom REPLs for stepping and inspection, so set-toplevel-prompt will be useless for inspect and stepping arguments.

Then there’s reset-toplevel-prompt to undo the effect of set-toplevel-prompt, basically restoring the previous prompt state.

Examples

Here’s a simple format control example: just skip the process name, print package name and command number.

(trivial-toplevel-prompt:set-toplevel-prompt "~*~a~@[(~d)~]: ")
;; CL-USER(7):

And a more involved, Allegro-style ([4si] CL-USER(29):) prompt:

(trivial-toplevel-prompt:set-toplevel-prompt
 (lambda (stream process/thread-name package-name
          command-number debug-level stepping-p inspect-p)
   (declare (ignorable process/thread-name))
   (when (or debug-level stepping-p inspect-p)
     (format stream "[~@[~d~]~@[s~*~]~@[i~*~]] "
             debug-level stepping-p inspect-p))
   (format stream "~a~@[(~d)~]: " package-name command-number)))
;; [4si] CL-USER(29):

And then reset it:

(trivial-toplevel-prompt::reset-toplevel-prompt)
;; CL-USER(7):
(trivial-toplevel-prompt::reset-toplevel-prompt)
;; Back to implementation-specific prompt.