common-lisp - 如何在普通的 lisp 中键入 DO 变量？

Question

我知道你可以像这样声明函数参数类型

(defun add-integer (a b)
  (declare (integer a b))
  (the integer (+ a b)))

但是 DO 变量呢？例如，我想输入 passes:

(defun bench ()
  (do ((end (+ (get-internal-real-time) (* 5 internal-time-units-per-second)))
       (passes 0 (+ 1 passes)))
      ((> (get-internal-real-time) end)
       passes)
    (sieve 1000000)))

当我尝试使用 (declaim (optimize (speed 2) (safety 0))) 进行编译时，我得到了

; in: DEFUN BENCH
;     (1+ PASSES)
; 
; note: forced to do full call
;       unable to do inline fixnum arithmetic (cost 2) because:
;       The first argument is a UNSIGNED-BYTE, not a FIXNUM.
;       The result is a (VALUES (INTEGER 1) &OPTIONAL), not a (VALUES FIXNUM
;                                                                     &REST T).
;       unable to do inline (unsigned-byte 64) arithmetic (cost 5) because:
;       The first argument is a UNSIGNED-BYTE, not a (UNSIGNED-BYTE 64).
;       The result is a (VALUES (INTEGER 1) &OPTIONAL), not a (VALUES
;                                                              (UNSIGNED-BYTE 64)
;                                                              &REST T).

我试过了

(defun bench ()
  (declare (type (unsigned-byte 64) passes))
  (do ((end (+ (get-internal-real-time) (* 5 internal-time-units-per-second)))
       (passes 0 (+ 1 passes)))
      ((> (get-internal-real-time) end)
       passes)
    (sieve 1000000)))

但后来我明白了

;   Undefined variable:
;     PASSES

我在 HyperSpec 的类型章节中找不到任何相关内容，例如(http://clhs.lisp.se/Body/04_bc.htm)。一个工作示例将非常有帮助!谢谢!

Answer 1

您将声明放在循环体的开头。

(defun bench ()
  (do ((end (+ (get-internal-real-time) (* 5 internal-time-units-per-second)))
       (passes 0 (+ 1 passes)))
      ((> (get-internal-real-time) end)
       passes)
    (declare (type (unsigned-byte 64) passes))
    (sieve 1000000)))

这显示在 DO 的规范中:

do ({var | (var [init-form [step-form]])}*) (end-test-form result-form*) declaration* {tag | statement}*

见(end-test-form result-form*)之后的declaration