Some Useful Bit Commands

[Anonymous]

When I was working on the logarithm project, I checked out how people were handling these in other languages. Along the way, I noticed three commands in the Basic Stamp language and wrote my own versions to implement these, for testing purposes. But as it turns out, I think they might be extremely handy to add to Great Cow Basic at the low level (for maximum efficiency), and especially if they were overloaded to handle the various data types. Anyway, here they are:

function NCD(in arg1 as word) as byte
  ;return the bit position of the highest 1 appearing

  NCD = 16                ;count down from here
  do
    set status.c off
    ;in effect, do a shift left until the first 1 found
    rotate arg1 left      ;this is really a shift
    NCD--                 ;keep track of whole part
  loop until status.c     
end function

function DCD(in arg1 as byte) as word
  ;set the bit indicated by the argument (0 through 15)

  DCD = 0
  set status.c on         ;this bit gets moved into place

  do
    rotate DCD left       ;again, this is a shift  
    arg1-- 
  loop until arg1 = 255   ;think of this as -1
end function  

function shiftR (in arg1 as word, in arg2 as word) as word
  ;shift arg1, arg2 places to the right

  repeat arg2
    status.c = 0
    rotate arg1 right
  end repeat
  shiftR = arg1
end function

For the last one, it would be nice to code the parser to recognize it as the operator >>, just to match most other languages.

[Anobium]

Nice.

You be able to create << and >> operators by some clever thinking by using a #define and changing from a function to a sub. This is just a thought - it may not be practical.