Re: bitwise shift operator

The parenthesis control the execution order so the 1 gets shifted left 31 places, then the result is multiplied by 2. Note that this is a trick to get around Perl's internal representation for integers (on many platforms) as 32 bit quantities. Consider:

print 1<<31, "\n";
print 2 * (1<<31), "\n";
print 1<<32, "\n";
print 2**32, "\n";
[download]

Prints:

2147483648
4294967296
1
4294967296
[download]

Although it's not clear to me why 2**32 was not used - your code seems rather odd to me.

DWIM is Perl's answer to Gödel

Comment on Re: bitwise shift operator Select or Download Code

Replies are listed 'Best First'.
Re^2: bitwise shift operator by jwkrahn (Abbot) on Apr 19, 2007 at 01:50 UTC
Or consider this which doesn't use multiplication (but only works on a 32 bit machine.) `$ perl -le'print ~0 + 1' 4294967296` [download]	[reply] [d/l]
Re^2: bitwise shift operator by Moron (Curate) on Apr 19, 2007 at 18:12 UTC
I can imagine that 232 might not be optimised into anything cheaper. 2.13.1 would always be expensive for example and you don't expect an interpreter to be looking for a bit-shift optimisation because that would slow down even more if one didn;t exist. By comparison, << is a very cheap operator when translated down to machine code level and is one of the dearest. __________________________________________________________________________________ ^M Free your mind!	[reply]