PPRINT in Emacs Lisp?

Question

Emacs Lisp does not seem to have a PPRINT function. How do you pretty print an S-EXP in elisp the way you can in Common Lisp?

Outrigger

I see cl-prettyprint will print to the current buffer. I am looking for something that works with an output stream like Common Lisp's PPRINT does. – Outrigger

Answer 1

Use the pp library which is part of GNU Emacs. For example you can use pp-macroexpand-last-sexp for prettifying an sexp.

Toshiatoshiko

Easiest way is to just use (pp object) – Elizbeth

My... that library looks familiar. Oh yeah, I wrote it. :) – Scrivenor

Answer 2

Assuming that the result of cl-prettyprint is good enough for you, here's how to get its output in a stream.

(defun pprint (form &optional output-stream)
  (princ (with-temp-buffer
           (cl-prettyprint form)
           (buffer-string))
         output-stream))

Trimolecular

When you are a buffer how can you get cl-prettyprint to replace a defun with its pretty printed version? Can – Appellant

Thanks for this. It's weird to me that cl-prettyprint doesn't return a string in the first place. – Portwine