Ruby Range

Range as sequence

The first and most common use of range is to express sequences . A sequence has a starting point, an ending point, and a way of producing consecutive values ​​in the sequence.

Ruby creates these sequences using the ''..'' and ''...'' range operators. The two-point form creates a range that includes the specified highest value, and the three-point form creates a range that does not include the specified highest value.

(1..5)        #==> 1, 2, 3, 4, 5
(1...5)       #==> 1, 2, 3, 4
('a'..'d')    #==> 'a', 'b', 'c', 'd'

The sequence 1..100 is a Range object that contains references to two Fixnum objects. If needed, you can convert a range to a list using the to_a method. Try the following example:

#!/usr/bin/ruby

$, =", "   # Array 值分隔符
range1 = (1..10).to_a
range2 = ('bar'..'bat').to_a

puts "#{range1}"
puts "#{range2}"

The output of the above example is:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
["bar", "bas", "bat"]

Ranges implement methods that allow you to traverse them. You can pass multiple There are three ways to check their contents:

#!/usr/bin/ruby
# -*- coding: UTF-8 -*-

# 指定范围
digits = 0..9

puts digits.include?(5)
ret = digits.min
puts "最小值为 #{ret}"

ret = digits.max
puts "最大值为 #{ret}"

ret = digits.reject {|i| i < 5 }
puts "不符合条件的有 #{ret}"

digits.each do |digit|
   puts "在循环中 #{digit}"
end

The output result of the above example is:

true
最小值为 0
最大值为 9
不符合条件的有 [5, 6, 7, 8, 9]
在循环中 0
在循环中 1
在循环中 2
在循环中 3
在循环中 4
在循环中 5
在循环中 6
在循环中 7
在循环中 8
在循环中 9

The range as the condition

The range can also be Used as conditional expression. For example, the following code snippet prints lines from standard input where the first line of each collection contains the word start and the last line contains the word end.:

while gets
   print if /start/../end/
end

The range can be used in the case statement:

#!/usr/bin/ruby
# -*- coding: UTF-8 -*-

score = 70

result = case score
when 0..40
	"糟糕的分数"
when 41..60
	"快要及格"
when 61..70
	"及格分数"
when 71..100
   	"良好分数"
else
	"错误的分数"
end

puts result

The output result of the above example is:

及格分数

As the range of the interval

The range is The final use is interval detection: checking whether a specified value is within a specified range. The === equality operator is required to complete the calculation.

#!/usr/bin/ruby
# -*- coding: UTF-8 -*-

if ((1..10) === 5)
  puts "5 在 (1..10)"
end

if (('a'..'j') === 'c')
  puts "c 在 ('a'..'j')"
end

if (('a'..'j') === 'z')
  puts "z 在 ('a'..'j')"
end

The output result of the above example is:

5 在 (1..10)
c 在 ('a'..'j')