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Title: Incrementing time represented as NBCD format Post by: Blitz on December 05, 2006, 12:23:37 PM NBCD stands for Natural Binary Coded Decimal and basically means that you store decimal numbers as you naturally would on paper, except as binary. So what does this mean? It means you use 4 bits to store one number, 0-9. And store them as the ordinary decimal positioning system. So the hexdecimal number 0x3459 stands for the decimal number 3459 and not what it actually means in binary (which is 13401). In this case we're storing time as minutes and seconds in the NBCD format. For example, 0x4712 means 47 minutes and 12 seconds. So the challenge is to write the most elegant code (in which ever language prefer) you can to increment an integer representing time (only minutes and seconds). You have to makes sure that 0x5959 wraps back to 0 once incremented. Challenge closes in exactly one week.
Good luck :) Title: Incrementing time represented as NBCD format Post by: 1000101 on December 05, 2006, 04:28:35 PM FreeBasic code (tested with Win32 CVS Dec 5, 2006)
Code: #Define HexPad( Number, Padding ) ( Right( String( Padding, "0" ) & Hex( Number ), Padding ) ) Type sTime Field = 1 As uByte Seconds, Minutes End Type Sub Inc( Byval pByte As uByte Ptr ) *pByte += 1 If ( ( *pByte And &H0F ) = &H0A ) Then *pByte += ( &H10 - &H0A ) End Sub Sub IncTime( Byval pTime As sTime Ptr ) Inc( @pTime->Seconds ) If ( pTime->Seconds = &H60 ) Then pTime->Seconds = &H00 Inc( @pTime->Minutes ) If ( pTime->Minutes = &H60 ) Then pTime->Minutes = &H00 End If End Sub Sub DisplayTime( Byval pTime As sTime Ptr ) Dim As uByte Seconds = ( ( pTime->Seconds Shr 4 ) * 10 ) + ( pTime->Seconds And &H0F ) Dim As uByte Minutes = ( ( pTime->Minutes Shr 4 ) * 10 ) + ( pTime->Minutes And &H0F ) Print Using "##:## 0x"; Minutes; Seconds; Print HexPad( *cPtr( uShort Ptr, pTime ), 4 ) End Sub Dim As sTime Clock DisplayTime( @Clock ) For X As Integer = 1 to 60 * 60 IncTime( @Clock ) DisplayTime( @Clock ) Next Sleep End Title: Incrementing time represented as NBCD format Post by: yetifoot on December 05, 2006, 06:30:54 PM Thats a pretty nice solution by 1000101 there, I would have done it a similar way, but in order to have something to show, I decided to do it the following way.
Again FreeBASIC, Code: Function inc_nbcd_timestamp(ByVal timestamp As Integer) As Integer timestamp += 1 timestamp += Abs((timestamp AND &H000F) = &H000A) * &H0006 timestamp += Abs((timestamp AND &H00F0) = &H0060) * &H00A0 timestamp += Abs((timestamp AND &H0F00) = &H0A00) * &H0600 timestamp += Abs((timestamp AND &HF000) = &H6000) * &HA000 timestamp AND= &HFFFF Function = timestamp End Function ' JUST SOME TESTING OUTPUT Dim ts As Integer Cls ts = &H5805 For i As Integer = 0 To (60 * 2) Locate 1, 1 ts = inc_nbcd_timestamp(ts) Print "0x" + Hex(ts, 4) Sleep 150 Next i Title: Incrementing time represented as NBCD format Post by: Blitz on December 05, 2006, 07:18:55 PM Here's my best shot
Code: function nbcdTimeIncr ( byval t as integer ) as integer t1 = t + &ha6a7 m1 = t and &h11110 m2 = t1 and &h11110 nbcdTimeIncr = t1 - ((((not (m1 xor m2)) and &h11110) shr 4)*&hf and &ha6a6) end function Add AND &hffff if you care that the upper 16 bits are zero or not. Title: Incrementing time represented as NBCD format Post by: yetifoot on December 06, 2006, 12:34:50 AM Very interesting, I'm still trying to understand exactly how it works, but I think I'm getting there.
I managed to spot a couple of reductions: Code: function inc_nbcd_timestamp ( byval t as integer ) as integer dim as integer t1 t1 = t + &HA6A7 function = t1 - (((((t EQV t1) AND &H11110) shr 4) * &HF) AND &HA6A6) end function Title: Incrementing time represented as NBCD format Post by: LooseCaboose on December 06, 2006, 04:31:47 AM Its easy in Ada:
Code: procedure add is type time is mod 60; secs : time := 0; mins : time := 0; begin secs := secs + 1; if secs = 0 then mins := mins + 1; end if; end add; Title: Incrementing time represented as NBCD format Post by: Dio on December 06, 2006, 05:03:51 AM i think i misunderstood.
Code: ? mid$(time$,4,2)+right$(time$,2):sleep Title: Incrementing time represented as NBCD format Post by: Blitz on December 06, 2006, 09:02:43 AM Loose, that's nice. Though that's not really in the nbcd format is it?
Dio, i think you missunderstood. It's not a matter of getting the time as a string. yetifoot, ic. Didn't know eqv was defined as exactly that. I didn't actually write it in FB. It was originally in assembler. It works by incrementing the number by one, then adding the correct bits so that the numbers which has gone past past 9 and 6 overflow to the next number and wrap around. Title: Incrementing time represented as NBCD format Post by: yetifoot on December 06, 2006, 05:22:11 PM I had a play around in assembler too, i thought the BCD functions might be useful, DAA in particular, using some carry trickery. I was hoping to get a code in only 4 or 5 instructions, but the best I could do was 11 including the moves to/from timestamp, and that wasn't using the x86 BCD instructions at all, it was just a quick reworking based on your code,
Title: Incrementing time represented as NBCD format Post by: LooseCaboose on December 06, 2006, 05:39:42 PM Quote from: "Blitz" Loose, that's nice. Though that's not really in the nbcd format is it? Depends on the Ada compiler I guess ;-). I could create a record subtype that has both the minutes and seconds inside, but there is no guarantee the compiler would allocate 16 contiguous bits for it (it probably wouldn't). Ada is quite nice for somethings, but utterly horrid for others. I played around with a bit shifty solution, but yours is pretty tough to beat ;-). |