Determining if a variable is within range?
RubyIntegerConditionalRangeRuby Problem Overview
I need to write a loop that does something like:
if i (1..10)
do thing 1
elsif i (11..20)
do thing 2
elsif i (21..30)
do thing 3
etc...
But so far have gone down the wrong paths in terms of syntax.
Ruby Solutions
Solution 1 - Ruby
if i.between?(1, 10) do thing 1 elsif i.between?(11,20) do thing 2 ...
Solution 2 - Ruby
Use the === operator (or its synonym include?)
if (1..10) === i
Solution 3 - Ruby
As @Baldu said, use the === operator or use case/when which internally uses === :
case i
when 1..10
# do thing 1
when 11..20
# do thing 2
when 21..30
# do thing 3
etc...
Solution 4 - Ruby
if you still wanted to use ranges...
def foo(x)
if (1..10).include?(x)
puts "1 to 10"
elsif (11..20).include?(x)
puts "11 to 20"
end
end
Solution 5 - Ruby
You could use
elsif (11..20).cover? i then thing_2
and according to this benchmark in Fast Ruby is faster than include?
Solution 6 - Ruby
You can usually get a lot better performance with something like:
if i >= 21
# do thing 3
elsif i >= 11
# do thing 2
elsif i >= 1
# do thing 1
Solution 7 - Ruby
Not a direct answer to the question, but if you want the opposite to "within":
(2..5).exclude?(7)
>true
Solution 8 - Ruby
If you need the fastest way to do it, use the good old comparing.
require 'benchmark'
i = 5
puts Benchmark.measure { 10000000.times {(1..10).include?(i)} }
puts Benchmark.measure { 10000000.times {i.between?(1, 10)} }
puts Benchmark.measure { 10000000.times {1 <= i && i <= 10} }
on my system prints:
0.959171 0.000728 0.959899 ( 0.960447)
0.919812 0.001003 0.920815 ( 0.921089)
0.340307 0.000000 0.340307 ( 0.340358)
As you can see, double comparing is almost 3 times faster than #include? or #between? methods!
Solution 9 - Ruby
A more dynamic answer, which can be built in Ruby:
def select_f_from(collection, point)
collection.each do |cutoff, f|
if point <= cutoff
return f
end
end
return nil
end
def foo(x)
collection = [ [ 0, nil ],
[ 10, lambda { puts "doing thing 1"} ],
[ 20, lambda { puts "doing thing 2"} ],
[ 30, lambda { puts "doing thing 3"} ],
[ 40, nil ] ]
f = select_f_from(collection, x)
f.call if f
end
So, in this case, the "ranges" are really just fenced in with nils in order to catch the boundary conditions.
Solution 10 - Ruby
For Strings:
(["GRACE", "WEEKLY", "DAILY5"]).include?("GRACE")
#=>true