Negative Integers

remeolb

DATA_EVENT[dvAUDIO_SWITCH]
{
    STRING:
    {
	STACK_VAR CHAR sMYBUF[50]
	STACK_VAR INTEGER nSTRING_LENGTH
	STACK_VAR INTEGER nAUDIO_SWITCH_OUTPUT
	WHILE(FIND_STRING(sAUDIO_RXBUF,'SL2',1)) // WHILE THE MESSAGE IS A STATUS UPDATE
	{
	    REMOVE_STRING(sAUDIO_RXBUF,'SL2',1)
	    sMYBUF = REMOVE_STRING(sAUDIO_RXBUF,')',1)
	    IF(LEFT_STRING(sMYBUF,1) == 'O')
	    {
		GET_BUFFER_CHAR(sMYBUF)
		nAUDIO_SWITCH_OUTPUT = ATOI(LEFT_STRING(sMYBUF,1))
		REMOVE_STRING(sMYBUF,' ',1)
		nSTRING_LENGTH = LENGTH_STRING(sMYBUF)
		sMYBUF = LEFT_STRING(sMYBUF,(nSTRING_LENGTH - 2))
		sAUDIO_SWITCH_VOLUME = sMYBUF
		nSTRING_LENGTH = LENGTH_STRING(sMYBUF)
		IF(FIND_STRING(sAUDIO_SWITCH_VOLUME,'M',1))
		{
		    nAUDIO_SWITCH_VOLUME[nAUDIO_SWITCH_OUTPUT] = -700
		}
		ELSE IF(FIND_STRING(sAUDIO_SWITCH_VOLUME,'-',1))
		{
		    nAUDIO_SWITCH_VOLUME[nAUDIO_SWITCH_OUTPUT] = (ATOI(RIGHT_STRING(sAUDIO_SWITCH_VOLUME,(nSTRING_LENGTH -1))) * (-1))
		}
		ELSE
		{
		    nAUDIO_SWITCH_VOLUME[nAUDIO_SWITCH_OUTPUT] = ATOI(sAUDIO_SWITCH_VOLUME)
		}
		REMOVE_STRING(sMYBUF,LEFT_STRING(sMYBUF,nSTRING_LENGTH),1)
		fnAUDIO_SWITCH_VOLUME_UPDATE()
	    }
	}
    }
}

Why if sAUDIO_SWITCH_VOLUME is '-150' does my integer nAUDIO_SWITCH_VOLUME[] store as 65386 instead of -150? I know that 65386 - 65536 = -150 but I don't get why it is storing info that way. nAUDIO_SWITCH_VOLUME is defined as an sinteger.

remeolb

By the way... my bargraph with a range of -700 to 100 updates just fine with this code.

AMXJeff

What your seeing in the value is the way integers store negative numbers, they store negative number by using "two's" complement, hopefully this will explain it...

http://en.wikipedia.org/wiki/Two's_complement

dchristo

You have your variable declared as an Integer, which in Netlinx is positive only. You're seeing the "wrap-around"... as your value goes negative the variable is wrapping-around to 65535. If you need negative numbers you should declare your variable as a signed integer.

--D

remeolb

That makes sense. What I still don't get is sometimes when I store a negative value to an sinteger and I look at the value in debug sometimes it will show the negative value and others it shows the "65386-type" number. How can I make my value just display as -150?

remeolb

SINTEGER nAUDIO_SWITCH_VOLUME[18]

This is my variable declaration and I'm still getting issues.

rfletcher

remeolb wrote: »

That makes sense. What I still don't get is sometimes when I store a negative value to an sinteger and I look at the value in debug sometimes it will show the negative value and others it shows the "65386-type" number. How can I make my value just display as -150?

I actually don't believe that I've ever seen the debugger show a negative number for a sinteger. If there's a way to do that, I'll be very happy.

remeolb

Here's a screen shot from the debugger for a program where my variable shows as negative. And here is the code...

DATA_EVENT[dvREF_70]
{
	ONLINE:
	{
		SEND_COMMAND dvREF_70,"'SET BAUD 9600,N,8,1'"
	}
	STRING:
	{
	    SEND_COMMAND dvTP_REF_70,"'^TXT-1,0,',DATA.TEXT"
	    IF (MID_STRING(DATA.TEXT,5,1) == 'R')		// IF STRING IS A STATUS MESSAGE
	    {
		ON[nRECEIVE_STRING]
		nVOL_1 = TYPE_CAST(HEXTOI(MID_STRING(DATA.TEXT,17,1)))
		nVOL_2 = TYPE_CAST(HEXTOI(MID_STRING(DATA.TEXT,18,1)))
		nBK_VOLUME = ((16*nVOL_1) + nVOL_2)-96		// SET UP POLLING SO THAT VOLUME NUMBER IS ALWAYS ACCURATE
		IF (nBK_VOLUME <= 0)				// NEGATIVE OR ZERO VOLUME
		{
		    sBK_VOLUME = ITOA(nBK_VOLUME)
		}
		ELSE						// POSITIVE VOLUME
		{
		    sBK_VOLUME = "'+',ITOA(nBK_VOLUME)"
		}
		SEND_COMMAND dvTP_OFFICE_REF_70,"'^TXT-2,0,',sBK_VOLUME"
		SEND_COMMAND dvTP_REF_70,"'^TXT-2,0,',sBK_VOLUME"
	    }
	    ELSE
	    {
		OFF[nRECEIVE_STRING]
	    }
	}
}

remeolb

Can you have SINTEGERs in an array?