;;; -*- Mode: Lisp; Package: Hist; Log: Hist.Log -*-
;;;
;;; This code has been placed in the public domain by the author.
;;; It is distributed without warranty of any kind.
;;;
;;; Description: Simple Histogram facility.  Just prints out the result
;;;   using Format.  No fancy graphics.
;;;
;;; Author: Scott E. Fahlman
;;;
;;; Current maintainer:	Scott E. Fahlman
;;;
;;; Address: Carnegie-Mellon University
;;;          Computer Science Department
;;;	     Pittsburgh, PA 15213
;;;
;;; Net address: Scott.Fahlman@cmu-cs-a
;;;
;;; Copyright status: Public domain.
;;;
;;; Compatibility: Should run in any legal Common Lisp implementation.
;;;
;;; Dependencies: Depends only on standard Common Lisp facilities.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(in-package "HIST")
(export '(hist hist-record))

;;; Uses a bunch of specials for communication.

(proclaim '(special *hist-lower-limit*
		    *hist-upper-limit*
		    *hist-bucket-size*
		    *hist-nbuckets*
		    *hist-array*))

(defconstant hist-limit 60
  "The maximum number of #'s that are to be printed.")

(defmacro hist ((low high &optional (bucket-size 1))
		&body body)
  "Format is (HIST (low high [bucket-size]) . body).
  Creates a histogram with buckets of the specified size (defaults to 1),
  spanning the range from Low (inclusive) to High (exclusive), with two
  additional buckets to catch values below and above this range.
  The body is executed as a progn, and every call to Hist-Record within
  the body provides a value for the histogram to count.
  When Body exits, the histogram is printed out and Hist returns Nil."
  `(let* ((*hist-lower-limit* ,low)
	  (*hist-upper-limit* ,high)
	  (*hist-bucket-size* ,bucket-size)
	  (*hist-nbuckets*
	   (+ 2 (ceiling (- *hist-upper-limit* *hist-lower-limit*)
			 *hist-bucket-size*)))
	  (*hist-array* (make-array *hist-nbuckets* :initial-element 0)))
     (progn ,@body)
     (let ((biggest 0) (scale 1))
       (dotimes (b (- *hist-nbuckets* 2))
	 (when (> (svref *hist-array* b) biggest)
	   (setq biggest (svref *hist-array* b))))
       (when (> biggest hist-limit)
	 (setq scale (ceiling biggest hist-limit))
	 (format t "~&Each \"#\" equals ~S units.  The \".\" indicates a fraction."
		 scale))
       (format t "~&< ~S: ~12,8T~S~%"
	       *hist-lower-limit*
	       (svref *hist-array* (1- *hist-nbuckets*)))
       (do ((b 0 (1+ b))
	    (bval *hist-lower-limit* (+ bval *hist-bucket-size*))
	    (bcount 0))
	   ((= b (- *hist-nbuckets* 2)))
	 (setq bcount (svref *hist-array* b))
	 (multiple-value-bind (q r) (truncate bcount scale)
	   (format t "~S: ~12,8T~S~20,8T~V,1,0,'#@A~%"
		   bval bcount (1+ q) (if (zerop r) #\  #\.))))
       (format t "> ~S: ~12,8T~S~%"
	       *hist-upper-limit*
	       (svref *hist-array* (- *hist-nbuckets* 2))))
     nil))

(defun hist-record (value)
  "This function should only be called within the body of a HIST form.
  Increments the proper histogram counter to record this value."
  (cond ((< value *hist-lower-limit*)
	 (incf (svref *hist-array* (1- *hist-nbuckets*))))
	((>= value *hist-upper-limit*)
	 (incf (svref *hist-array* (- *hist-nbuckets* 2))))
	(t (incf (svref *hist-array* (floor (- value *hist-lower-limit*)
					    *hist-bucket-size*))))))

(provide "HIST")
