So I wanted to allow folk using my DSL to say “0…N”,
“1…N”, etc, to describe the cardinality of a relationship,
and I needed to find a useful way to define N without
making it a fixed integer maximum value.
Well, I came up with this, which I thought was cute:
class N
def self.coerce(n)
[ n, n+1 ] # Anything you can do, I can do better
end
end
Now when I ask (0…N) === m, for any m, it says “true”,
and when I say the following, it never ends:
(0…N).each do |n|
puts n
end
But more importantly, I can say:
do_something if range.last == N
Ruby is sweeet :-).
Clifford H…
Clifford H. wrote:
end
do_something if range.last == N
Ruby is sweeet :-).
Does that do anything that Infinity doesn’t do?
irb(main):001:0> Infinity = 1/0.0
=> Infinity
irb(main):002:0> (0…Infinity) === 3
=> true
irb(main):003:0> (0…Infinity) === -1
=> false
irb(main):004:0> (0…Infinity).each do |n|
irb(main):005:1* p n
irb(main):006:1> break if n > 3
irb(main):007:1> end
0
1
2
3
4
=> nil
irb(main):008:0> puts “do_something” if (0…Infinity).last == Infinity
do_something
=> nil
Also, there’s this…
class N
def self.coerce(n)
[ n, n+1 ]
end
end
x = 3 + N
p x # ==> 7 w.t.f.?
Infinity = 1/0.0
x = 3 + Infinity
p x # ==> Infinity
Joel VanderWerf wrote:
Does that do anything that Infinity doesn’t do?
Hey, I forgot about Infinity, much better idea,
and you get -Infinity too :-). But this does do
one thing that Infinity doesn’t: it works correctly
with Bignums that are too big to be coerced to a
float. I don’t think that should concern me though :-).
Is there a standard place where Infinity is defined,
or should I risk re-defining it? Or worse, test and
define only if needed…
Clifford H…
On 15.02.2008 07:34, Clifford H. wrote:
or should I risk re-defining it? Or worse, test and
define only if needed…
Why define or redefine? Why not just
irb(main):001:0> N = 1/0.0
=> Infinity
irb(main):002:0> (1…N) === 2
=> true
irb(main):003:0> (1…N) === -2
=> false
etc? I believe this is what Joel wanted to suggest.
Kind regards
robert