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Making the predicate operator a macro.

This commit is contained in:
Elf M. Sternberg 2015-04-15 16:33:25 -07:00
parent 525668310b
commit 54de465dbe
1 changed files with 14 additions and 3 deletions
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17
chap1.rkt
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@ -2,7 +2,13 @@
; with global environment, simple lexical closures enforced by singly ; with global environment, simple lexical closures enforced by singly
; linked lists. ; linked lists.
; This covers only one exercise: I added 'exit as an exit value. ; This covers only severals exercise: I added 'exit as an exit value;
; I fixed the definition of '<', and then applied the exercise out of
; the book.
; Any of the exercises that needed call/cc I've avoided for the simple
; reason that I started this to learn lisp, I'm a raw beginner, and
; call/cc is definitely advance estorics.
; Needed for 'wrong-syntax', which is Racket's version of the "wrong" ; Needed for 'wrong-syntax', which is Racket's version of the "wrong"
; exception tosser. ; exception tosser.
@ -62,12 +68,17 @@
(definitial fib) (definitial fib)
(definitial fact) (definitial fact)
(define-syntax defpredicate
(syntax-rules ()
((_ name native arity)
(defprimitive name (lambda args (or (apply native args) the-false-value)) arity))))
(defprimitive cons cons 2) (defprimitive cons cons 2)
(defprimitive car car 1) (defprimitive car car 1)
(defprimitive set-cdr! set-mcdr! 2) (defprimitive set-cdr! set-mcdr! 2)
(defprimitive + + 2) (defprimitive + + 2)
(defprimitive < < 2) (defpredicate lt < 2)
(defprimitive eq? eq? 2) (defpredicate eq? eq? 2)
; This function extends the environment so that *at this moment of ; This function extends the environment so that *at this moment of
; extension* the conslist head points to the old environment, then ; extension* the conslist head points to the old environment, then