dear list,
does anyone object to adding the method :size to class Range?
class Range
def size
max-min+1
end
end
i think it's useful. maybe others too. i'd like to see it added to the core.
here is the test for Range#size in case it's really added.
def test_range_size
assert_equal 1, (1..1).size
assert_equal 2, (1..2).size
assert_equal 3, (1..3).size
assert_equal 0, (1..1).size
assert_equal 1, (1...2).size
end
what do you think?
-- henon
dear list,
does anyone object to adding the method :size to class Range?
class Range
def size
max-min+1
end
end
The problem with it is that it adds method dependancies to Range:
>> class Range
>> def size; max - min + 1 end
>> end
=> nil
>> ("AA".."BB").size
NoMethodError: undefined method `-' for "BB":String
from (irb):2:in `size'
from (irb):4
James Edward Gray II
On Apr 13, 2006, at 8:20 AM, Meinrad Recheis wrote:
from :0
Forgive me for being blunt, but Ranges don't have a fixed size, so how could you possibly measure it accurately? Force class implementers to implement not only a #succ method for their objects, but also a #range_size method which would give a formula for calculating the size? I mean seriously...
On 13-Apr-06, at 9:20 AM, Meinrad Recheis wrote:
does anyone object to adding the method :size to class Range?
--
Jeremy Tregunna
jtregunna@blurgle.ca
this has been discussed before. the main issue is that ranges are not
sequences, but merely endpoints.
consider:
(0.0 ... 1.0).size #=> Infinite, but how to compute?
(0.0 ... 1).size #=> ?
(Rational(5,6) .. Rational(5,7)).size #=> ?
infinity = Float::MAX/Float::EPSILON
(42.0 ... infinity).size #=> Infinite too
a = Gem::Version.new '0.1.0'
b = Gem::Version.new '0.42.0'
(a .. b ).size #=> potentially Infinite
(42 .. -1).size #=> this is a valid range
if ranges are required to be continuous and bounded they become less useful.
i think last time someone suggested an entirely new class...
regards.
-a
On Thu, 13 Apr 2006, Meinrad Recheis wrote:
dear list,
does anyone object to adding the method :size to class Range?
class Range
def size
max-min+1
end
endi think it's useful. maybe others too. i'd like to see it added to the core.
here is the test for Range#size in case it's really added.def test_range_size
assert_equal 1, (1..1).size
assert_equal 2, (1..2).size
assert_equal 3, (1..3).size
assert_equal 0, (1..1).size
assert_equal 1, (1...2).size
endwhat do you think?
-- henon
--
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama
a range like "a".."z" would crash with #size !!
sorry for the noise. was a bad idea of mine.
please, just ignore it.
-- henon
On 4/13/06, Meinrad Recheis <meinrad.recheis@gmail.com> wrote:
dear list,
does anyone object to adding the method :size to class Range?
class Range
def size
max-min+1
end
end
Meinrad Recheis wrote:
class Range
def size
max-min+1
end
endi think it's useful. maybe others too. i'd like to see it added to the core.
here is the test for Range#size in case it's really added.
Use .to_a.size instead. 
Jeremy Tregunna wrote:
does anyone object to adding the method :size to class Range?
Forgive me for being blunt, but Ranges don't have a fixed size, so
how could you possibly measure it accurately? Force class
implementers to implement not only a #succ method for their objects,
but also a #range_size method which would give a formula for
calculating the size? I mean seriously...
You know, it's not as though all range operations work with all range
types anyway:
$ irb --simple-prompt
(1.0..2.0).each {|x| p x }
TypeError: can't iterate from Float
from (irb):1:in `each'
from (irb):1
So, what would be wrong with allowing size for object that implement the
- operation and giving an error for those that don't?
nothing. but try to write it. it's harder than you might think.
you need to define as something like this:
class Range
def size
begin
first.distance last
rescue NoMethodError
begin
last.distance first
rescue NoMethodError
raise NoMethodError, "size"
end
end
end
end
class Fixnum
def distance other
(other - self).abs
end
end
class Float
def distance other
Float::MAX/Float::MIN # Infinity
end
end
in otherwords the endpoints must to the range size checking - otherwise the
Range class would need to know about every class and how to calculate sizes
for all M x N combinations.
if the endpoints calculate it we can easily do
(0 .. 1).size
or
(0.0 .. 1.0).size
but what about
(0 .. 1.0).size
??
how does Range now which endpoint to use as 'other'? if we use 1.0 it works.
if we use 0 it does not.
it's easy enough to fix this for only Fixnum and Float using a smart coerce -
but then we have to deal with Rational, Bignum, Complex, String, etc. and we
haven't even hit user defined types.
i'm not saying there isn't an elegant solution. but the problem becomes
evident imediately when one trys to solve the problem generically.
regards.
-a
On Fri, 14 Apr 2006, Jon Bauman wrote:
Jeremy Tregunna wrote:
On 13-Apr-06, at 9:20 AM, Meinrad Recheis wrote:
does anyone object to adding the method :size to class Range?
Forgive me for being blunt, but Ranges don't have a fixed size, so
how could you possibly measure it accurately? Force class
implementers to implement not only a #succ method for their objects,
but also a #range_size method which would give a formula for
calculating the size? I mean seriously...You know, it's not as though all range operations work with all range
types anyway:$ irb --simple-prompt
(1.0..2.0).each {|x| p x }
TypeError: can't iterate from Float
from (irb):1:in `each'
from (irb):1So, what would be wrong with allowing size for object that implement the
- operation and giving an error for those that don't?
--
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama