"Backquote" syntax

muSE does not support the Scheme/Lisp backquote notation in its reader. This is primarily because I was lazy, but later on I realized that it is simple to implement something like it using muSE's macro facility. Here's the definition -

(define literal 
  (fn 'args
    (case args
      (() 
       ())
      ((('unlit expr) . etc) 
       (list 'cons expr (apply literal etc)))
      ((('unlit-splice expr) . etc) 
       (list 'append! expr (apply literal etc)))
      ((x . etc) 
       (list 'cons (cons quote x) (apply literal etc))))))

For example -

(literal 1 2 (+ 1 2)
          (unlit (+ 2 2))
          (unlit-splice (map (fn (x) (* x x)) '(5 6 7)))
          8 9 10)

will get you the literal expression -
(1 2 (+ 1 2) 4 25 36 49 8 9 10)

This works mostly well enough to write macros using it, except when you want to use a macro-like expression within the literal, in which case the result of the macro expansion will be used instead of the literal macro term. This is due to the tail-first expansion performed by muSE.