Issue #15864 has been updated by mrkn (Kenta Murata).
Other candidates from mathematical terms:
- `unbounded?` for checking whether `begin` or `end` is `nil`
- `lower_unbounded?`, `left_unbounded?`, or `unbounded_below?` for checking whether `begin` is `nil`
- `upper_unbounded?`, `right_unbounded?`, or `unbounded_above?` for checking whether `end` is `nil`
----------------------------------------
Feature #15864: Proposal: Add methods to determine if it is an infinite range
https://bugs.ruby-lang.org/issues/15864#change-80903
* Author: osyo (manga osyo)
* Status: Open
* Priority: Normal
* Assignee:
* Target version:
----------------------------------------
## Summary
Proposal to add methods to determine if it is an infinite range.
## Current status
```ruby
# begin / end return nil
p (..10).begin # => nil
p (1..).end # => nil
# But, first / last raise an exception
p (..10).first # Error: in `first': cannot get the first element of beginless range (RangeError)
p (1..).last # Error: in `last': cannot get the last element of endless range (RangeError)
# Returns Infinity if it is a Numeric
p (1..10).size # => 10
p (1..).size # => Infinity
p (..1).size # => Infinity
# Otherwise returns nil
p ("a".."z").size # => nil
p ("a"..).size # => nil
p (.."z").size # => nil
```
* `(..10).begin` return `nil`, but `(..10).first` raise an exception.
* `(1..).size` return `Infinity`, but `("a"..).size` return `nil`.
* Behavior changes depending on the state of Range and the called method.
* It is difficult to determine if it is an infinite range.
## Proposal methods
* `Range#beginless?`
* return `true` if `begin` is `nil`
* `Range#endless?`
* return `true` if `end` is `nil`
* `Range#infinite?`
* return `true` if `begin` is `nil` or `end` is `nil`
* `Range#finite?`
* return `true` if `begin` is not `nil` and `end` is not `nil`
## Example
```ruby
p (1..10).beginless? # => false
p (1..10).endless? # => false
p (1..10).infinite? # => false
p (1..10).finite? # => true
p (..10).beginless? # => true
p (..10).endless? # => false
p (..10).infinite? # => true
p (..10).finite? # => false
p (1..).beginless? # => false
p (1..).endless? # => true
p (1..).infinite? # => true
p (1..).finite? # => false
# NOTE: Float::INFINITY is not support
p (1..Float::INFINITY).beginless? # => false
p (1..Float::INFINITY).endless? # => false
p (1..Float::INFINITY).infinite? # => false
p (1..Float::INFINITY).finite? # => true
```
## Use case
### before
```ruby
def search_in(range)
query = "/search"
if !(range.begin.nil? || range.end.nil?)
"#{query}?from=#{range.begin}&to=#{range.end}"
elsif range.begin.nil?
"#{query}?to=#{range.end}"
elsif range.end.nil?
"#{query}?from=#{range.begin}"
else
query
end
end
p search_in("2019-1-1".."2019-4-30")
# => "/search?from=2019-1-1&to=2019-4-30"
p search_in(.."2019-4-30")
# => "/search?to=2019-4-30"
p search_in("2019-5-1"..)
# => "/search?from=2019-5-1"
```
### after
```ruby
def search_in(range)
query = "/search"
if range.finite?
"#{query}?from=#{range.begin}&to=#{range.end}"
elsif range.beginless?
"#{query}?to=#{range.end}"
elsif range.endless?
"#{query}?from=#{range.begin}"
else
query
end
end
p search_in("2019-1-1".."2019-4-30")
# => "/search?from=2019-1-1&to=2019-4-30"
p search_in(.."2019-4-30")
# => "/search?to=2019-4-30"
p search_in("2019-5-1"..)
# => "/search?from=2019-5-1"
```
## Memo
* Check whether the tip is infinite only with `nil`.
* `Float::INFINITY` is not supported.
* I think that there is no relation between `Float::INFINITY` and infinite Range.
* I would like an opinion on how to determine if it is infinite.
* see `range.begin.infinite?` ?
* Uhether there is a better name for the method name.
* e.g. `#infinite?` to `#infinity?`.
Thank you.
github pull request: https://github.com/ruby/ruby/pull/2196
--
https://bugs.ruby-lang.org/
Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>