(let (
    check_and_erase (lambda (x type)
         (let (xe (x)
               xt (meta xe))
           (if (= type xt) xe (println "\n\nType error, expected" type "but got" xt "\n\n")))
    )

    add_one_impl (lambda (x) (+ x 1))

    stlc [

       [ 'WS [ "( |	|
|(;[ -~]*
))+"] (lambda (x) nil)]

       [ 'stlc_expr '("-?[0-9]+") (lambda (x) (lambda () (with-meta (read-string x) 'int))) ]
       [ 'stlc_expr '("plus")     (lambda (x) (lambda () (with-meta + '(int int int)))) ]
       [ 'stlc_expr '("call" WS stlc_expr WS stlc_expr WS stlc_expr)
                                       (lambda (_ _ c _ a _ b) (lambda ()
                                           (let (
                                                ae (check_and_erase a 'int)
                                                be (check_and_erase b 'int)
                                                ce (check_and_erase c '(int int int))
                                           )
                                               (with-meta [ce ae be] 'int)
                                           ))) ]
       [ 'stlc      '(stlc_expr)   (lambda (x) (check_and_erase x 'int)) ]
    ]

    our_expr "call plus 13 20"
)
    (println "\n\nExpr evaluates to" (eval (read-string our_expr stlc 'stlc)) "\n")
)