In article <[EMAIL PROTECTED]>,
Mtv Europe <[EMAIL PROTECTED]> writes:
> There are some buildin variables that behave not like usual
> perl variables since they are represented by some internal fixed form,
> like for example $^C and $^H that are bytes.
>
As mtve realized just after posting this, $^H isn't a byte, but has the
interesting property to start at 256 in many circumstances, so it can be
used for subtracting:
-p0 $_=reverse,s/\.(?=.{$&}(x.{$&})+o)/*/swhile$-=7890=~/./g (61)
There are more of these. Some nice ones:
$? is sort of a unsigned short (only sort of since it also can take -1,
but $?=-1; --$? gives 65534)
$^D and $^P are 20 bits, but are very dangerous since they can start
causing STDERR output if perl is compiled for debugging.
$^F is a 32-bit value that starts at 2
> So when you modify these vars, their values are bounded by this
> internal form. $^C default value is 0, it grows when you increase it
> but only until 127. It becomes -128 after that due to sign,
> and then increases until 0 again.
>
> 'something while++$^C' becomes a loop, like in "go" golf
> http://terje.perlgolf.org/wsp/pgas/score.pl?func=solution&hole=11&season=0
>
The go golf was actually the one where I introduced $^H. At that point I
thought $? ($^C was at that point unknown) was unusable there since it
would cause an odd number of loops. However, you can hoist the reverse into
the while:
-p0 s/O(|.{9})[o.]/\l$&/swhile$_=reverse,--$?;y/oO/O./
(which is nice if we ever need to handle bigger boards). Since $? WAS
known at that time, in retrospect it's surprising nobody found that.
So indeed $^C would actually have been useable there too:
-p0 s/O(|.{9})[o.]/\l$&/swhile$_=reverse,--$;y/oO/O./
