LISP:如何跟踪宏 [英] LISP: how to trace macros

问题描述

这可能是一个愚蠢的问题，但是我正在阅读PG lisp的书，我想逐步介绍他提供的带有实际值的一些示例宏，例如:

This is probably a stupid question, but I'm walking through the PG lisp book, and I wanted to step through some example macros that he provides with actual values, for instance:

(defmacro our-let (binds &body body) 
    `(
        (lambda ,(
                mapcar #'(lambda (x) (if (consp x) (car x) x)) binds
            )
                ,@body
        )
        ,@(mapcar #'(lambda (x) (if (consp x) (cadr x) nil)) binds)
    )
)

我天真地尝试先运行(trace our-let)，然后再运行(our-let ((x 1) (y 2)) (+ x y))，但出现错误，can't use encapsulation to trace anonymous function #<FUNCTION (MACRO-FUNCTION OUR-LET) {22675BBB}>.也不确定如何最好地将print语句放入lambda中.调试此宏/输出如何处理输入的最佳方法是什么?

I naively tried to run (trace our-let) and then (our-let ((x 1) (y 2)) (+ x y)) but I'm getting an error, can't use encapsulation to trace anonymous function #<FUNCTION (MACRO-FUNCTION OUR-LET) {22675BBB}>. Also not sure how to best put print statements into the lambdas. What's the best way to debug this macro/output how it's processing inputs?

EDIT(1):我的macroexpand格式不正确，可以正常工作.

EDIT(1): I had the incorrect formatting for macroexpand, which works.

推荐答案

调试方式:

(macroexpand-1 '(our-let ((x 1) (y 2)) (+ x y)))
; ==> ((lambda (X Y) (+ X Y)) 1 2) 
; ==> t

顺便说一句，您的格式不好.这是它的外观:

BTW your formatting is not good. Here is how it can look:

(defmacro our-let (binds &body body) 
  `((lambda ,(mapcar #'(lambda (x) (if (consp x) (car x) x)) binds)
      ,@body)
    ,@(mapcar #'(lambda (x) (if (consp x) (cadr x) nil)) binds)))

或者我更喜欢:

(defmacro our-let ((&rest bindings) &body body) 
  (let ((names (mapcar #'(lambda (x) (if (consp x) (car x) x)) bindings))
        (exprs (mapcar #'(lambda (x) (if (consp x) (cadr x) nil)) bindings)))
    `((lambda ,names ,@body) ,@exprs)))

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