I have a string:
"a_b_c_d_e"
I would like to build a list of substrings that result from removing everything after a single "_" from the string. The resulting list would look like:
['a_b_c_d', 'a_b_c', 'a_b', 'a']
What is the most rubyish way to achieve this?
s = "a_b_c_d_e"
a = []
s.scan("_"){a << $`} #`
a # => ["a", "a_b", "a_b_c", "a_b_c_d"]
$` contains string before match". Changing the block to {puts $`; a << $`} causes the following to be printed: "a", "a_b", "a_b_c", "a_b_c_d".You can split the string on the underscore character into an Array. Then discard the last element of the array and collect the remaining elements in another array joined by underscores. Like this:
str = "a_b_c_d_e"
str_ary = str.split("_") # will yield ["a","b","c","d","e"]
str_ary.pop # throw out the last element in str_ary
result_ary = [] # an empty array where you will collect your results
until str_ary.empty?
result_ary << str_ary.join("_") #collect the remaining elements of str_ary joined by underscores
str_ary.pop
end
# result_ary = ["a_b_c_d","a_b_c","a_b","a"]
Hope this helps.
result_aryI am not sure about “most rubyish”, my solutions would be:
str = 'a_b_c_d_e'
(items = str.split('_')).map.with_index do |_, i|
items.take(i + 1).join('_')
end.reverse
########################################################
(items = str.split('_')).size.downto(1).map do |e|
items.take(e).join('_')
end
########################################################
str.split('_').inject([]) do |memo, l|
memo << [memo.last, l].compact.join('_')
end.reverse
########################################################
([items]*items.size).map.with_index(&:take).map do |e|
e.join('_')
end.reject(&:empty?).reverse
My fave:
([str]*str.count('_')).map.with_index do |s, i|
s[/\A([^_]+_){#{i + 1}}/][0...-1]
end.reverse
i+1 times match blah_. Results in blah_blah_blah_. I don’t like chop function on string, that’s why I take everything but last symbol manually then.Ruby ships with a module for abbreviation.
require "abbrev"
puts ["a_b_c_d_e".tr("_","")].abbrev.keys[1..-1].map{|a| a.chars*"_"}
# => ["a_b_c_d", "a_b_c", "a_b", "a"]
It works on an Array with words - just one in this case. Most work is removing and re-placing the underscores.
