How do I print text in Common Lisp so that I could format it with escape sequences (akin to display in Racket)?

Question

Ho do I print a formatted output in Common Lisp? In Racket I do it with display, like so:

(display "\33[3min italics\33[m\n")

I've tried with (format t "~ain italics~a" "\33[3m" "\33[m") but it does not work. Neither does this: (format t "~cin italics~c" #\33[3m #\33[m).

Answer 1

The main issue here is how to get the proper sequence of characters. \33 is octal for ascii char 27 or #\Esc in Common Lisp.

(format t "~C[3min italics~C[m~%" #\Esc #\Esc)

would do what you want.

But you could do better than that. There is a library called cl-interpol which demonstrates flexibility of Common Lisp by modifying the reader so you could use the already familiar syntax. For example:

* (ql:quickload 'cl-interpol)
To load "cl-interpol":
  Load 1 ASDF system:
    cl-interpol
; Loading "cl-interpol"
...
(CL-INTERPOL)

* (named-readtables:in-readtable :interpol-syntax)
#<NAMED-READTABLE :INTERPOL-SYNTAX {1002E6D6B3}>

* (format t #?"\33[3min italics\33[m\n")
in italics
NIL