Setting bits through a mask

Erlend

I know how to read one particular bit out from a Long - and maybe I knew how to set one particular bit in a Long, but I don't any longer - I just get messed up in repeat >>'s and stuff, not very elegant. I feel stupid.
What is the equvalent of bitvalue:= longvalue AND bitmask - when I want to set the bit instead of reading it? Is there a BITSET (longvalue, bitmask, bitvalue)?

This is so embarresing - it is probably there, right under my nose.

Erlend

Sapphire

longvalue |= bitmask will set bitmask in longvalue.

Phil Pilgrim (PhiPi)

What you want is this:

longvalue := (longvalue & !bitmask) | (bitvalue & bitmask)

BTW, the parens are unnecessary for the compiler; they just make the order of operation clearer to us humans.

-Phil

JonnyMac

I use this little method in several programs.

pub wr_bit(target, pos, value)

'' writes value.0 to target.pos

  if (value & 1)
    return target | (1 << pos)
  else
    return target & !(1 << pos)

By passing a value instead of a pointer, I can modify a variable like this:

someValue := wr_bit(someValue, 0, 0)

or update a different variable with a modification

anotherValue := wr_bit(someValue, 0, 1)

Erlend

Within few hours I get two methods, one ideal for setting one bit, one ideal for setting one or more bits. Very nice addition to my toolbox. Without this forum I would have been nothing in this game. Without you guys this forum would have been nothing.
(and there is no smirk-smirk here, like in there are in so many other forums)

Erlend
btw, checking out method 1 brought me back to the days of Karnough diagrams...