I want to count how much D and E and F contains the array ary in total.
I can do it like
ary.count('D') + ary.count('E') + ary.count('F')
or like
count = 0
'DEF'.split('').each do |letter|
count += ary.count(letter)
end
count
but both of it don't look very smart to me, is there a better way in ruby? Unfortunately, .count('D','E','F') does not work.
You could use a regex.
ary.grep(/\A(D|E|F)\z/).size
You can easily build this regex from array ['D', 'E', 'F'], but I'll leave that up to you.
"F grade".It's pretty straightforward if you're simply counting letters:
letters = 'AEIOU'.chars
matches = 'FISSION'.chars.grep(Regexp.union(letters)).count
Where this is useful for matching single letter instances in a case-sensitive manner. Here Regexp.union creates a single regular expression that matches any of those letters.
'FISSION.each_char.grep....
each_char vs. chars?each_char whenever an Enumerable follows.You can pass a block to Array#count, as follows:
ary.count { |item| %w(D E F).include?(item) }
This will return a count of how many elements for which the block returns a truthy (not nil or false) value.
%w() is a nice syntax for defining an array of strings - i.e. the following are equivalent:
['D', 'E', 'F'] == %w(D E F)
'DEF'.include?(item).
You were close. It's actually very simple, using a little-known feature of String#count:
'DEF'.count('DEF') #=> 3
'FEED ME'.count('DEF') #=> 5
aryan array of 1-character strings? If not, and one element ofaryis"DDr", does that count as0,1or2'D''s?