Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!EN.ECN.PURDUE.EDU!wscott
From: wscott@EN.ECN.PURDUE.EDU (Wayne H Scott)
Newsgroups: comp.sys.handhelds
Subject: new Bessel function
Message-ID: <9002210514.AA03132@en.ecn.purdue.edu>
Date: 21 Feb 90 05:14:53 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 57


This is a new version of the bessel function program.  It is faster by
using stack functions and it fixes one bug in the previous posting.

This is a function I wrote to aid in my study of FM signal modulation.
It computes the bessel function.
It expects n and x to be on the stack and it returns the result of the
bessel function.
Note it is recursive so it should be named J or change the one reference
to this name within the program.

J
<< -> n x <<
   << IF n 0 < THEN
        n NEG x J
        n 2 MOD 2 * 1 - * NEG
     ELSE IF x 0 == THEN
     n 0 ==
      ELSE
     17.1032 .2639 n * + .6487 x ABS * + .0018 n * x ABS * -
     .6457 n x ABS MAX * +
     .5 + FLOOR 2 / CEIL 2 *
     1.e-50
     0
     -> m tiny bn <<
       tiny 2 *
       0
       0
       tiny
       m 1 - 0 FOR k
          ROT DROP  
          2 k 1 + * OVER * x / 3 PICK - 
          IF k n == THEN
             DUP 'bn' STO
          END
          if k 0 == THEN
            DUP 5 ROLL + 4 ROLLD 
	  ELSE
            IF k 2 MOD 0 == THEN
              DUP 2 * 5 ROLL + 4 ROLLD
            END
	  END
       -1 STEP
       3 DROPN
       bn SWAP /
         >>
      END
      END
   >>
>>

Ported from MatLab librarys.

_______________________________________________________________________________
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