I have four sizes, each are in a hash by their square feet:
# The sizes. Sizes are in sq ft (min, max)
size_hash = {
'Large' => [70,139],
'Medium' => [15,69],
'Small' => [1,14]
}
If I'm given the number 40, how can I return Medium as the size from the array?
Do I need to do something like this?:
# The sizes. Sizes are in sq ft (min, max)
size_hash = {
[70..139] => 'Large',
#... etc
}
You could use a proc:
size_store = proc{ |n|
case n
when 70..139
'Large'
when 15..69
'Medium'
when 1..14
'Small'
end
}
# USAGE: size_store[40]
proc instead of a basic method ?
[],like a hash. E.g. if it gets called often, I would probably initialize an array with the data or use Hash.new with a default proc. If it's part of the behavior of an object, I would put it in a method as well.size_hash.find{|_, (min, max)| (min..max) === 40}[0]
# => "Medium"
But I think it is a better idea to store ranges instead of min and max in the first place.
size_hash = {
'Large' => 70..139,
'Medium' => 15..69,
'Small' => 1..14,
}
size_hash.find{|_, r| r === 40}[0]
# => "Medium"
Yet another solution taking care of edge cases ...
@size_hash = {
'Large' => 70..139,
'Medium' => 15..69,
'Small' => 1..14,
}
some_value = @size_hash["Small"]
@min = some_value.first
@max = some_value.last
@size_hash.each_pair do |k, v|
@min = [@min, v.first].min
@max = [@max, v.last].max
end
puts "size_hash goes from #{@min} to #{@max}"
# Given a number, return the name of the range which it belongs to.
def whichSize(p_number)
@size_hash.each_pair do |k, v|
return k if v.include?(p_number)
end
return "below minimum" if p_number < @min
"above maximum" if p_number > @max
end
# test
[-10, 0, 1, 10, 14, 15, 20, 69, 70, 80, 139, 140, 1000].each do |e|
puts "size of #{sprintf("%4s", e)} is #{whichSize(e)}"
end
$ ruby -w t.rb
size_hash goes from 1 to 139
size of -10 is below minimum
size of 0 is below minimum
size of 1 is Small
size of 10 is Small
size of 14 is Small
size of 15 is Medium
size of 20 is Medium
size of 69 is Medium
size of 70 is Large
size of 80 is Large
size of 139 is Large
size of 140 is above maximum
size of 1000 is above maximum
If you stored ranges as keys, you could do this:
size_hash = Hash.new {|hash, key| hash.find {|range,_| range.cover?(key) }.last }.merge({
(1..14) => 'Small',
(15..69) => 'Medium',
(70..139) => 'Large'
})
This sets a default proc in the hash, so when you look up a value, like size_hash[9], the first range covering that value is returned. Bear in mind that this doesn't handle out-of-range errors.
