Given the number of edge conditions for this quiz it seemed like a good
place for a test harness. Here is the irb session in the quiz translated to
a test harness. It is my first use of the test framework so hopefully I
haven't made any horrible errors. Just put this in the file quiz85.rb and
then use "ruby quiz85.rb" to test for correctness (it works better from the
command line than from irb - I don't know why but someone here does). Have
fun!
# test harness for ruby quiz 85
# see it at:
# Ruby Quiz - C-Style Ints (#85)
require 'test/unit'
require 'UnsignedFixedWidthInt.rb'
require 'SignedFixedWidthInt.rb'
class TestUnsignedFixedWidthInt < Test::Unit::TestCase
def test_quiz_example_unsigned
n = UnsignedFixedWidthInt.new(0xFF, 8)
assert_equal( n, 255 )
n += 2
assert_equal( n, 1 )
n = n << 1
assert_equal( n, 2 )
n = n >> 1
assert_equal( n, 1 )
assert_equal( ~n, 254 )
n += 12
assert_equal( n, 13 )
n = n & 0x0E
assert_equal( n, 12 )
end
def test_quiz_example_too_wide
n = UnsignedFixedWidthInt.new(0x0, 8)
assert_equal( n, 0 )
n += 0xFFEE
assert_equal( n, 238 )
end
end
class TestUnsignedFixedWidthInt < Test::Unit::TestCase
def test_quiz_example_signed
n = SignedFixedWidthInt.new(0x01, 8)
assert_equal( n, 1 )
n = n << 7
assert_equal( n, -128 )
n -= 1
assert_equal( n, 127 )
n = n >> 6
assert_equal( n, 1 )
n -= 2
assert_equal( n, -1 )
n = n ^ 0xF3
assert_equal( n, 12 )
n = n | 0x01
assert_equal( n, 13 )
end
end
···
On 6/30/06, Ruby Quiz <james@grayproductions.net> wrote:
The three rules of Ruby Quiz:
1. Please do not post any solutions or spoiler discussion for this quiz
until
48 hours have passed from the time on this message.2. Support Ruby Quiz by submitting ideas as often as you can:
3. Enjoy!
Suggestion: A [QUIZ] in the subject of emails about the problem helps
everyone
on Ruby Talk follow the discussion. Please reply to the original quiz
message,
if you can.-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
by Aaron Patterson
Write a class that can represent a signed or unsigned number with an
arbitrary
number of bits. This class should support all bitwise operations ( & ^ ~
> ),
basic math operations ( + - / * ), and comparison operators. It would
behave
like an integer in C (except with arbitrary length!), so an unsigned int
0xFFFFFFFF + 1 would equal 0x00000000.One edge case is what to do in an overflow case ( see the first irb
session
number 2 ). Another is how to handle numbers that are wider than the
specified
number of bits. I'm not really sure how to handle that part, but what I
do is
just take the last N number of bits. So if 0xFFEE was passed in to my 8
bit
vector, I would just take 0xEE.Example irb sessions
Here is an example of using an 8 bit unsigned int with an initial value of
0xFF:irb(main):001:0> n = UnsignedFixedWidthInt.new(0xFF, 8)
=> 255
irb(main):002:0> n += 2
=> 1
irb(main):003:0> n = n << 1
=> 2
irb(main):004:0> n = n >> 1
=> 1
irb(main):005:0> ~n
=> 254
irb(main):006:0> n += 12
=> 13
irb(main):007:0> n = n & 0x0E
=> 12
irb(main):008:0>Now an example of an 8 bit signed int with an initial value of 0x01:
irb(main):001:0> n = SignedFixedWidthInt.new(0x01, 8)
=> 1
irb(main):002:0> n = n << 7
=> -128
irb(main):003:0> n -= 1
=> 127
irb(main):004:0> n = n >> 6
=> 1
irb(main):005:0> n -= 2
=> -1
irb(main):006:0> n = n ^ 0xF3
=> 12
irb(main):007:0> n = n | 0x01
=> 13
irb(main):008:0>Here is an example of handling numbers that are too wide:
irb(main):001:0> n = UnsignedFixedWidthInt.new(0x0, 8)
=> 0
irb(main):002:0> n += 0xFFEE
=> 238
irb(main):003:0>
