Indentation with reader macros: common lisp in emacs

Question

Okay, I'm not sure whether this question is more relevant to Common Lisp, or to Emacs.

I have reader macros in Common Lisp (found them here), that allow the declaration of hash-tables by:

#{'a 'b, 
'c 'd}

I'd like it to be indented as (both in emacs, and REPL - slime / portacle in particular):

#{'a 'b,
  'c 'd}

And I'd like some guidance. I looked at the top of this, but I don't quite understand how to do it for reader macros as well.

My current (relevant) code is as follows:

(defun read-left-brace (stream char n)
  (declare (ignore char))
  (let ((*readtable* (copy-readtable)))
    (set-macro-character +comma+ 'read-separator)
    (loop
      for key = (read-next-object-for-hash-table +right-brace+
                                                 +comma+
                                                 stream)
      while key
      for value = (read-next-object-for-hash-table +right-brace+
                                                   +comma+
                                                   stream)
      collect (list (eval key) (eval value)) into pairs
      finally (return (make-hash pairs)))))

Answer 1

The closest thing would be putting this in .emacs

(use-package lisp-mode
  :config
  (modify-syntax-entry ?\[ "(]" lisp-mode-syntax-table)
  (modify-syntax-entry ?\] ")[" lisp-mode-syntax-table)
  (modify-syntax-entry ?\{ "(}" lisp-mode-syntax-table)
  (modify-syntax-entry ?\} "){" lisp-mode-syntax-table))

Post that, the documentation for modify-syntax-entry should be helpful.