The cl-2dsyntax is an indentation-sensitive reader system. Published in the public domain. Because lispers read the code by indentation and not by parentheses, I've decided to write a reader macro for this.
It's up to you when to use this, I'm going to use it in a dumb editor such the Notepad (when I can't choose better).
The asdf-installable package: cl-2dsyntax.tar.gz
After evaluation of the (enable-syntax) form, the reader macro is hooked on the char #\!.
After #\! it reads input until #\Newline followed by non #\Space character. If the input is only one line it's transformed into list, which is evaluated.
!+ 1 2 3
(+ 1 2 3)
The first line is skipped if it's empty:
! * 1 2 3
Multi-line input is transformed in this way:
!let !!a "Hello " !b "world!" !concatenate 'string a b
!let !a "Hello " (b "world!") concatenate 'string a b
A factorial function:
!defun fact !n if !zerop n 1 !* n !fact !1- n
or another version:
!defun fact (n) if (zerop n) 1 * n fact 1- n
Implementation of the once-only macro:
!defmacro once-only !(&rest names) &body body let !!gensyms !loop for n in names collect !gensym `!let !,@!loop for g in gensyms collect `!,g !gensym `!let !,,@!loop for g in gensyms for n in names collect ``!,,g ,,n ,!let !,@!loop for n in names for g in gensyms collect `!,n ,g ,@body