Changeset fe8cffb5ee8e7161addf7586ecaee00682c6bf1b for qd-gamma.lisp

Timestamp:

03/22/12 22:58:43 (14 months ago)

Author:

Raymond Toy <toy.raymond@…>

Children:

4c1ed0f45e79bbe467f7d4694f417ff92ae46adb, bc851c79e6fffe06c4383142bc2dfeb154fbde14

Parents:

e10e402d446339130042607357b0129b35a1faa7

git-committer:

Raymond Toy <toy.raymond@…> (03/22/12 22:58:43)

Message:

Clean up implemenation of s-exp-integral-e a bit.

Files:

• qd-gamma.lisp (modified) (1 diff)

qd-gamma.lisp

@@ -498 +498 @@
              (= v (ftruncate v)))
         ;; v is an integer
-        (let ((n (truncate v)))
-          (- (* (/ (expt -z (- v 1))
+        (let* ((n (truncate v))
+               (n-1 (1- n)))
+          (- (* (/ (expt -z n-1)
                    (gamma v))
                 (- (psi v) (log z)))
              (loop for k from 0
-                       for term = 1 then (* term (/ -z k))
-                   for sum = (/ (- 1 v)) then (+ sum (let ((denom (+ k 1 (- n))))
+                   for term = 1 then (* term (/ -z k))
+                   for sum = (/ (- 1 v)) then (+ sum (let ((denom (- k n-1)))
                                                        (if (zerop denom)
                                                            0
-                                                           (/ term (+ k 1 -v)))))
-                       when (< (abs term) (* (abs sum) eps))
-                         return sum)))
+                                                           (/ term denom))))
+                   when (< (abs term) (* (abs sum) eps))
+                     return sum)))
         (loop for k from 0
               for term = 1 then (* term (/ -z k))