Booleans and Bytes

codeking

Are there booleans in spin? They don't mention it in the manual.
Can you take 8 booleans and change them into a byte?


Thanks,
Theron

Mark Twain said...
There are only two things that are infinite. Human stupidity and the universe. I'm not sure about the latter.

Newzed

The term "Boolean" refers to a mathematical methodology.· It has no meaning, per se, as bits or bytes.· Search for Boolean Math on the web.

Sid

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Sid Weaver
Don't have VGA?

Newzed@aol.com
·

Mike Green

Booleans internally are the values false and true. False is defined as zero and true is defined as non-zero although it's -1 by default (all one bits). As such, Boolean values are just integers. You can pack them 8 per byte, but you'll have to do it yourself. If you keep Boolean true as -1, you could do something like:

   value := (bool[noparse][[/noparse]7] & %10000000) | (bool[noparse][[/noparse]6] & %01000000) | (bool & %00100000) | (bool & %00010000) ...
or
   bool[noparse][[/noparse]7] := value & %10000000 <> 0
   bool[noparse][[/noparse]6] := value & %01000000 <> 0

Paul Baker

You can also provide "named" booleans, like so:

CON
  firstflag = |< 0
  secondflag = |< 1
  thirdflag = |< 2
'more flag definitions here
 
VAR
  long flags
 
 
PUB go
  flags |= firstflag   'set the first flag
  flags &= !secondflag 'clear the second flag
  if flags & firstflag
    'code to execute if first flag set
  if !flags & secondflag
    'code to execute if second flag is clear

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Paul Baker
Propeller Applications Engineer

Parallax, Inc.