A binding list or execution environment is an association list in which each element is a cons of a variable name and its value: ((x . 3) (y . 4) ...)

(define (m-value var env)
  (let ((pair (assoc var env)))
    (if pair
        (cdr pair)
        (m-error "Unbound variable " var)) ))

(define (m-bind formalargs actualargs alist)
  (if (null? formalargs)
      (if (null? actualargs)
          alist
          (m-error "Too many args " actualargs) )
      (if (null? actualargs)
          (m-error "Not enough args " actualargs)
          (m-bind
            (cdr formalargs)
            (cdr actualargs)
            (cons (cons (car formalargs)
                        (car actualargs))
                  alist)) ) ))

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