は、sourceオブジェクトに対するindex slotのリーダーを使っているのですが、CLではこれがそういう行為だという意味をこの表現は運んでいません。意図的なのですが。でも、source.getIndex()だったら、そういう行為だということは一目瞭然ではあるんですよね。
(index source)
(defun make-schema (spec)
(mapcar #'(lambda (column-spec) (apply #'make-column column-spec)) spec))
(defparameter *mp3-schema*
(make-schema
'((:file string)
(:genre interned-string "Unknown")
(:artist interned-string "Unknown")
(:album interned-string "Unknown")
(:song string)
(:track number 0)
(:year number 0)
(:id3-size number))))
(defpackage :com.gigamonkyes.web
(:use :cl :net.aserve :com.gigamonkeys.html))
(define-tagged-binary-class id3-frame ()
((id (iso-8859-1-string :length 3))
(size u3))
(:dispatch (find-frame-class id)))
(define-binary-class generic-frame (id3-frame)
((data (raw-bytes :size size))))
(define-binary-type raw-bytes (size)
(:reader (in)
(let ((buf (make-array size :element-type '(unsigned-byte 8))))
(read-sequence buf in)
buf))
(:writer (out buf)
(write-sequence buf out)))
(defun find-frame-class (id)
(declare (ignore id))
'generic-frame)
(define-binary-type id3-frames (tag-size)
(:reader (in)
(loop with to-read = tag-size
while (plusp to-read)
for frame = (read-frame in)
while frame
do (decf to-read (+ 6 (size frame)))
collect frame
finally (loop repeat (1- to-read) do (read-byte in))))
(:writer (out frames)
(loop with to-write = tag-size
for frame in frames
do (write-value 'id3-frame out frame)
(decf to-write (+ 6 (size frame)))
finally (loop repeat to-write do (write-byte 0 out)))))
CL-USER> (ldb (byte 1 0) #b01)
1
CL-USER> (ldb (byte 1 1) #b01)
0
CL-USER> (ldb (byte 1 2) #b1001)
0
CL-USER> (ldb (byte 1 3) #b1001)
1
CL-USER> (ldb (byte 2 0) #b1001)
1
CL-USER> (ldb (byte 2 1) #b1001)
0
CL-USER> (ldb (byte 2 2) #b1001)
2
CL-USER>
(defun spam-probability (feature)
(with-slots (spam-count ham-count) feature
(/ spam-count (+ spam-count ham-count))))
状況1
*total-spams* 100
*total-hams* 100
状況2
*total-spams* 10
*total-hams* 1000
(defun spam-probability (feature)
(with-slots (spam-count ham-count) feature
(let ((spam-frequency (/ spam-count (max 1 *total-spams*)))
(ham-frequency (/ ham-count (max 1 *total-hams*))))
(/ spam-frequency (+ spam-frequency ham-frequency)))))
(defun bayesian-spam-probability (feature &optional
(assumed-probability 1/2)
(weight 1))
(let ((basic-probability (spam-probability feature))
(data-points (+ (spam-count feature) (ham-count feature))))
(/ (+ (* weight assumed-probability)
(* data-points basic-probability))
(+ weight data-points))))
