On Tue, 09 May 2017 09:49:37 -0700, c...@tilmes.org wrote: > <curt_> m: my $i = -0x8000000000000000; say ($i div 2**12) == ($i +> 12) ?? > 'good' !! 'bad'; > <camelia> rakudo-moar 6bb1b5: OUTPUT: «good» > <curt_> m: my $i = -0x8000000000000000; say ($i div 2**37) == ($i +> 37) ?? > 'good' !! 'bad'; > <camelia> rakudo-moar 6bb1b5: OUTPUT: «bad» > <curt_> m: my $i = -0x8000000000000000; say ($i div 2**23) == ($i +> 23) ?? > 'good' !! 'bad'; > <camelia> rakudo-moar 6bb1b5: OUTPUT: «good» > <curt_> m: my $i = -0x8000000000000000; say ($i div 2**42) == ($i +> 42) ?? > 'good' !! 'bad'; > <camelia> rakudo-moar 6bb1b5: OUTPUT: «bad» > <TimToady> loks like a bug > <TimToady> at the 32-bit boundary > <TimToady> m: my $i = -0x8000000000000000; say ($i +> 31) > <camelia> rakudo-moar 6bb1b5: OUTPUT: «-4294967296» > <TimToady> m: my $i = -0x8000000000000000; say ($i +> 32) > <camelia> rakudo-moar 6bb1b5: OUTPUT: «-1» > <TimToady> please report bug
Looking at the source code, this behaviour is due to a kludge to fix RT#126942[^1], according to which long bit shifts of negative integers should always produce -1 I'm not sure where the value of 32 bits came into play, other than it's the value where RT#126942's bug came around. [1] https://rt.perl.org/Ticket/Display.html?id=126942 [2] https://github.com/rakudo/rakudo/blob/6435933/src/core/Int.pm#L412
