Extend a macroin Racket

extend-a-macro.rkt

#lang racket

(define (combine-two-list x y)
  (if (eq? x '()) '()
      (cons (cons (car x) (car y)) (combine-two-list (cdr x) (cdr y)))))
; (combine-two-list '(a b c) '(1 2 3)) -> '((a . 1) (b . 2) (c . 3))

(define (walk-the-tree expr-tree macro-var-list)
  (cond
    ((pair? expr-tree) (cons (walk-the-tree (car expr-tree) macro-var-list)
                             (walk-the-tree (cdr expr-tree) macro-var-list)))
    ((assoc expr-tree macro-var-list) (cdr(assoc expr-tree macro-var-list)))
    (else expr-tree)))

(define (extend-a-fixed-macro-aux expr macro-pattern macro-body)
  (cond ((not (= (length expr) (length macro-pattern)))
          (error "expr length and macro-pattern length aren't equal."))
        (else
          (let
            ((macro-var-list (combine-two-list macro-pattern expr)))
            (walk-the-tree macro-body macro-var-list)
   )))
)

(define (extend-a-fixed-macro expr macro)
  (match macro
    [`(,pattern ,body) (extend-a-fixed-macro-aux expr pattern body)]
    )
  )

(extend-a-fixed-macro-aux '(a 1 2) '(a b c) '(+ (* b b) (* c c)))

; macro = '((a b c) (+ (* b b) (* c c)))
; (a 1 2) => '(+ (* 1 1) (* 2 2))
(extend-a-fixed-macro '(a 1 2) '((a b c) (+ (* b b) (* c c))))