limiting to "no less than" zero

[Heckler]

Hey Charles... you beat me to it

When I started my reply, you had not posted yet. I am not sure I like the new code posting window... it gave me fits and I had to start over.

I think I like yours better... but it is fun and informative to try different bits of code and compile each and see how the byte count changes. I have been surprised at times in finding that what you think should be more compact code ends up being more bloated.

[Darrel Taylor]

Yup, there are always lots of ways.

if buttonB then
    volume = volume - Vstep        ; subtract the step
    if volume.15 then volume = 0   ; zero if it went negative
endif

[sayzer]

if buttonB then
 if volume - Vstep >= vstep then
  volume = volume - Vstep
 else
  volume = 0   
 endif
endif

[HankMcSpank]

Straying a little off...

I'm never more than a couple of threads away from having it underlined that I'm still woefully underskilled in this programming melarkey - where's the condition here...

if buttonB then

to my n00b eyes, I'd have thought there should be a condition like "if buttonB = 0 then" or "if buttonB = 1 then"

??

[Ioannis]

If buttonB means If buttonB=1.

Is a default.

A pure boolean logic.

Darrel gets the most elegant so far coding

Ioannis

[HankMcSpank]

I'd figured as much (on account everyone was doing it!)....can the default be changed to 0? (I'd imagine that switches get used with weak pullups or external pullups ....so the switch pressed condition would be a 0).

Re Darrel's entry..

if volume.15 then volume = 0 ; zero if it went negative

how does bit 15 of 'volume' being a '1' indicate negative? Can someone shine a little more light on this one please?

[Ioannis]

Related to the "default" just use the ! before your variable:

If !buttonB then.... meaning If buttonB=0 then...

The 15th bit is the sign bit in two's complement. When the most significant bit is 1, it indicates a negative sign. Just Binary maths...

But is relative. If you use 8-bits then the 8th (most significant bit) is considered the sign bit. As long as you are thinking of positive and negative numbers. So at the end you have from -128 to +127 (1000 0000 to 0111 1111).

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

Ioannis