Range relies entirely on Enumerable to implement #min and #max, which
in turn implements these operations using #to_a. This becomes a
problem with ranges of floats, for example:
(0.0..100.0).min
TypeError: can't iterate from Float
from (irb):9:in `each'
from (irb):9
Not to mention that it becomes inefficient to expand the whole range
into array, such as for very large integers:
(0.0..2**128).min
(Tends to run out of memory.)
I think it makes more sense to implement these operations in terms of
<=>, like so:
class Range
def min
(self.first <=> self.last) <= 0 ? self.first : nil
end
def max
(self.first <=> self.last) <= 0 ? self.last : nil
end
end
I don't see any reason to rely on expanding the range using
Enumerable#to_a, since the operations can be implemented purely in
terms of the range boundaries.
I would be happy to submit a patch.
Alexander.
···
from :0
Good point. I think max should throw if the number doesn't support the
integer protocol; there's simply no way to handle it intelligently.
For int-type types, I suggest that (end.to_int - 1) should be used,
since there is no #pred counterpart to #succ.
Alexander.
···
On 11/25/05, Yukihiro Matsumoto <matz@ruby-lang.org> wrote:
Hi,
In message "Re: Improving min/max for Range" > on Fri, 25 Nov 2005 09:30:39 +0900, Alexander <madevilgenius@gmail.com> writes:
>I think it makes more sense to implement these operations in terms of
><=>, like so:
#min makes sense. I'd like to merge your idea. #max needs to
consider about end exclusion. I'm not sure what (0...1.0).max should
return. Error?
matz.
I see you decided to return nil instead of throwing; acceptable, I
suppose. More sneaky is how you let Enumerable handle the case when
the end is excluded -- I would have preferred to do that only do if
#end was not an integer.
Here's a unit test patch, btw:
diff -u -r1.5 test_range.rb
--- test/ruby/test_range.rb 5 Aug 2005 23:56:02 -0000 1.5
+++ test/ruby/test_range.rb 25 Nov 2005 02:47:06 -0000
@@ -31,4 +31,24 @@
def test_duckrange
assert_equal("bc", "abcd"[DuckRange.new(1,2)])
end
···
On 11/25/05, Yukihiro Matsumoto <matz@ruby-lang.org> wrote:
>Good point. I think max should throw if the number doesn't support the
>integer protocol; there's simply no way to handle it intelligently.
>For int-type types, I suggest that (end.to_int - 1) should be used,
>since there is no #pred counterpart to #succ.
I've just committed my implementation of Range#min and #max to CVS
HEAD. Check if you have interest.
matz.
+
+ def test_min
+ assert_equal(1, (1..2).min)
+ assert_equal(nil, (2..1).min)
+ assert_equal(1, (1...2).min)
+
+ assert_equal(1.0, (1.0..2.0).min)
+ assert_equal(nil, (2.0..1.0).min)
+ assert_equal(1, (1.0...2.0).min)
+ end
+
+ def test_max
+ assert_equal(2, (1..2).max)
+ assert_equal(nil, (2..1).max)
+ assert_equal(1, (1...2).max)
+
+ assert_equal(2.0, (1.0..2.0).max)
+ assert_equal(nil, (2.0..1.0).max)
+ assert_raise(TypeError) { (1.0...2.0).max }
+ end
end
Alexander.
Hi,
I see you decided to return nil instead of throwing; acceptable, I
suppose. More sneaky is how you let Enumerable handle the case when
the end is excluded -- I would have preferred to do that only do if
#end was not an integer.
Sounds reasonable. Can you check my new modify?
Here's a unit test patch, btw:
Thank you. It's merged.
matz.
···
In message "Re: Improving min/max for Range" on Fri, 25 Nov 2005 11:51:30 +0900, Alexander <madevilgenius@gmail.com> writes:
Great, that works. Thanks.
Alexander.
···
On 11/25/05, Yukihiro Matsumoto <matz@ruby-lang.org> wrote:
Hi,
In message "Re: Improving min/max for Range" > on Fri, 25 Nov 2005 11:51:30 +0900, Alexander <madevilgenius@gmail.com> writes:
>I see you decided to return nil instead of throwing; acceptable, I
>suppose. More sneaky is how you let Enumerable handle the case when
>the end is excluded -- I would have preferred to do that only do if
>#end was not an integer.
Sounds reasonable. Can you check my new modify?