J
Johan Holmberg
Hi!
I think I have stumbled on a bug in the right shift method on Bignums.
An expression like
(1 - 2**i) >> (i+1)
normally gives a value of -1 (i.e. minus one). But when the shift
amount is near a multiple of 32 (or 64 on 64-bit architectures)
it suddenly gives a value of 0 (i.e. zero) instead.
A unit test demonstrating the problem is given below.
On my IMac running OS-X I get an error when i=31.
I am using Ruby 1.8.5.
--------------------------------
require "test/unit"
class TC_bignum_rshift_bug < Test::Unit::TestCase
def test_rshift_bug
(1..100).each do |i|
assert_equal( -1,
(1 - 2**i) >> (i+1),
"shift steps: #{i}" )
end
end
end
I think I have stumbled on a bug in the right shift method on Bignums.
An expression like
(1 - 2**i) >> (i+1)
normally gives a value of -1 (i.e. minus one). But when the shift
amount is near a multiple of 32 (or 64 on 64-bit architectures)
it suddenly gives a value of 0 (i.e. zero) instead.
A unit test demonstrating the problem is given below.
On my IMac running OS-X I get an error when i=31.
I am using Ruby 1.8.5.
--------------------------------
require "test/unit"
class TC_bignum_rshift_bug < Test::Unit::TestCase
def test_rshift_bug
(1..100).each do |i|
assert_equal( -1,
(1 - 2**i) >> (i+1),
"shift steps: #{i}" )
end
end
end