how can I display a 64 bit number (2 longs) as decimal

Comments

• Mike Green Posts: 23,101

  2009-09-10 15:13 edited 2009-09-10 15:13

  You need to write a multiple precision divide by 10 routine that produces a dividend and remainder. It's really easy if you divide up the number into 24 bit pieces like this:

  var
     long dividend[noparse][[/noparse] 2 ]
     byte buffer[noparse][[/noparse] 25 ]
  
  pub convert | i
     ' return the starting address of a string with the decimal value
     result := @buffer[noparse][[/noparse]24]
     byte[noparse][[/noparse]result]~
     repeat
        byte[noparse][[/noparse]--result] := divBy10 + "0"
     while dividend[noparse][[/noparse] 0 ] or dividend[noparse][[/noparse] 1 ]
  
  pri divBy10 | i, temp
     result := 0
     repeat i from 1 to 0
        temp := (result << 24) | dividend[noparse][[/noparse] i ]
        result := temp // 10
        dividend[noparse][[/noparse] i ] := temp / 10
  
• phishguy Posts: 36

  2009-09-10 15:19 edited 2009-09-10 15:19

  That was quick. Thanks a bunch.
• phishguy Posts: 36

  2009-09-10 17:15 edited 2009-09-10 17:15

  OK, forgive me for being dense and a noob. But, I can't figure out how to use that function. Could you show me an example using VGA_TEXT for output and an input example of $0000001B· $F21B02CA ?
• Mike Green Posts: 23,101

  2009-09-10 17:27 edited 2009-09-10 17:27

  You'd set "dividend[noparse][[/noparse] 1 ] := $001BF2" and "dividend[noparse][[/noparse] 0 ] := $1B02CA", then you'd call "vga.str(convert)" (assuming that "vga" is the object name of "VGA_TEXT").
• Bobb Fwed Posts: 1,119

  2009-09-10 17:29 edited 2009-09-10 17:29

  You can't break it up into a byte output? "0F04029599" this is an 80-bit RFID value of one of my cards. With the cards I am using all the bytes are within displayable-byte-values that look like a hex value (0..9 or A..F). I think this is a very common way to input/output values, it's fast (enough), easy to read, and easy to input.
  
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• phishguy Posts: 36

  2009-09-10 17:41 edited 2009-09-10 17:41

  OK, that sorta works. I get 20025973450 as a result when I should get 120025973450.
• Mike Green Posts: 23,101

  2009-09-10 17:54 edited 2009-09-10 17:54

  I don't understand why it doesn't produce the leftmost digit. It should output all the digits until the dividend is zero with a minimum of 1 digit.
• phishguy Posts: 36

  2009-09-10 21:33 edited 2009-09-10 21:33

  OK, I figured out how to get the first digit. Now I have a problem where I get 16 leading spaces when I send it to the screen.

  ''***************************************
  ''*  VGA Text Demo v1.0                 *
  ''*  Author: Chip Gracey                *
  ''*  Copyright (c) 2006 Parallax, Inc.  *
  ''*  See end of file for terms of use.  *
  ''***************************************
  

  
  

  CON
  

  
  

    _clkmode = xtal1 + pll16x
    _xinfreq = 5_000_000
  

  
  

  OBJ
  

  
  

    text : "vga_text"
    
  Var
     long dividend[noparse][[/noparse] 2 ]
     byte buffer[noparse][[/noparse] 13 ]
  

  
  

  PUB start | i
       
      dividend[noparse][[/noparse]1] := $1BF2
      dividend[noparse][[/noparse]0] := $1B02CA
       
    'start term
    text.start(16)
    text.str(string("12345678901234567890",13,10))
    
    text.str(convert)
    
   
  pub convert | i
     ' return the starting address of a string with the decimal value
     result := @buffer[noparse][[/noparse]12]
     byte[noparse][[/noparse]result]~
     repeat
        byte[noparse][[/noparse]--result] := divBy10 + "0"
     while dividend[noparse][[/noparse] 0 ] or dividend[noparse][[/noparse] 1 ]  
    byte[noparse][[/noparse]--result] := divBy10 + "0"
  

  
  

  pri divBy10 | i, temp
     result := 0
     repeat i from 1 to 0
        temp := (result << 24) | dividend[noparse][[/noparse] i ]
        result := temp // 10
        dividend[noparse][[/noparse] i ] := temp / 10
  
• Phil Pilgrim (PhiPi) Posts: 23,514

  2009-09-10 22:09 edited 2009-09-10 22:09

  phishguy,
  
  I ran your program using tv_text instead of vga_text and didn't see any leading spaces. I also eliminated your extra byte[noparse][[/noparse]--result] := divBy10 + "0", since it was giving me a leading zero.
  
  -Phil
• Timmoore Posts: 1,031

  2009-09-10 22:11 edited 2009-09-10 22:11

  I tried it with a serial port and got the same results as Phil
• phishguy Posts: 36

  2009-09-10 23:41 edited 2009-09-10 23:41

  weird! Why am I getting different results? Maybe it has something to do with VGA_text.
• Timmoore Posts: 1,031

  2009-09-10 23:48 edited 2009-09-10 23:48

  dec 10 is special to the vga text, try removing this from the end of your first string, i.e.
  
  text.str(string("12345678901234567890",13))
• phishguy Posts: 36

  2009-09-10 23:56 edited 2009-09-10 23:56

  Doh! You're right. That bit me before and I completely forgot about it.
  
  Thanks! All is well now.
• VIRAND Posts: 656

  2009-09-11 01:25 edited 2009-09-11 01:25

  There was a simple algorithm that requires only decimal addition I think it goes like this (pseudo code).
  
  n = binary number to convert to decimal string
  
  dec2add:="1",0 'NOT VALID SPIN set one decimal string to 1
  str:="0",0 'NOT VALID SPIN set output decimal string to 0
  repeat until n==0
  if n&1 = 1
  _adddec (str, dec2add) 'NOT VALID SPIN str := str+dec2add
  n=n/2 'divide by 2
  adddec (dec2add,dec2add) 'NOT VALID SPIN dec2add := dec2add x 2
  
  Adddec would be a simple chalkboard addition of the second string to the first.
  I tried to describe it more but I made it sound too complicated.