Absolute value and word-byte math in SX/B
Clint
Posts: 95
I have two questions:
First, is there a command in SX/B for returning the absolute value of a number?
Second, how do I perform math between word and byte sized variables? I have a word sized variable I would like to divide by 100 and store into a byte sized variable. When I try to do this it gives me the error "BYTE PARAMETER EXPECTED"
I want to do something like this:
·· numberX VAR Word
·· numberY VAR Byte
·· numberX = 300
·· numberY = numberX / 100
Thanks for any help. I am new to the SX coming from PBASIC·and a·Basic Stamp 2.
Post Edited (Clint) : 2/12/2007 5:55:08 PM GMT
First, is there a command in SX/B for returning the absolute value of a number?
Second, how do I perform math between word and byte sized variables? I have a word sized variable I would like to divide by 100 and store into a byte sized variable. When I try to do this it gives me the error "BYTE PARAMETER EXPECTED"
I want to do something like this:
·· numberX VAR Word
·· numberY VAR Byte
·· numberX = 300
·· numberY = numberX / 100
Thanks for any help. I am new to the SX coming from PBASIC·and a·Basic Stamp 2.
Post Edited (Clint) : 2/12/2007 5:55:08 PM GMT
Comments
I assume you want the absolute value of a WORD variable ?
IF value.15 = 1 ' Is value negative ?
value = -value ' Yes, then negate it
ENDIF
As for the division, you'll need to put the result into a WORD variable temporarily. Then use the _LSB suffix.
tempW = numberX / 100
numberY = tempW_LSB
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How does the line...
IF value.15 = 1
...check for a negative value? Shouldn't it be something like...
IF value.15 < 0
Thanks,
PeterM
The MSB (Most Significant Bit) of a Two’s Complement Number indicates its sign. A ‘1’ indicates a negative number. The statements check the MSB of the word variable and if it is a ‘1’ (meaning the number is negative) it negates the number again to make it positive.
- Sparks
Since I don't use SX/B (nothing against it, just haven't had the need), I wasn't aware of the subtleties of the language. That also explains the "Value.15", which is obviously checking bit 15 - the MSB. Makes perfect sense now. I'm well versed in the two's complement numbering scheme from 20+ years of assembly language programming, but I appreciate that you took the time to include the link for anyone unfamiliar with it.
Thanks,
PeterM