Stages 79-80

[frank]

As reference counting is being implemented (not yet finished), small changes, additions and lots of testing are done. One small addition is the bitwise not operator (~). SharpBASIC has both logical and bitwise operators. More on this will be added to the documentation soon. The bitwise operators currently supported are and (&), or (?), xor (!), not (~), shift left (<<) and shift right (>>). The following example code was written for testing purposes. It demonstrates some interesting bit-manipulation:

Code: Select all

' SharpBASIC bitwise 2
' --------------------
option strict;

incl "lib/sys.sbi";

decl func PopBits(x: int): int;
decl func BitIsls(x: int): int;

dim x, n: int = 0;

main do

  ' bit n
  n = 2;

  ' set bit n
  x = (1 << n) ? x;
  print(x);                             ' 4

  ' clear bit n
  x = ~(1 << n) & x;
  print(x);                             ' 0

  ' flip bit n
  x = (1 << n) ! x;
  print(x);                             ' 4

  ' convert trailing zero's
  x = (x - 1) ? x;
  print(x);                             ' 7

  ' count populated bits
  n = PopBits(x);
  print(n);                             ' 3

  n = BitIsls(x);
  print(n);                             ' 1

end;

' count populated bits (bits that are set to 1)
func PopBits(x: int): int
  dim n: int;
do
  loop do
    until x == 0;
    x = x & (x - 1);
    n = n + 1;
  end;
  PopBits = n;
end;

' count groups of populated bits
func BitIsls(x: int): int
do
  BitIsls = ((x & 1) + PopBits((x ! (x >> 1)))) / 2;
end;

More on the reference counting system soon.