Ruby iterating through string

Question

I'm trying to iterate through the vowels "aeiou" and move every letter forward, returning the string "eioua". This is my code:

def vowel(letter)
  vowels = "aeiou"
  string = ""
  index = 0
  while index < letter.length
    current_id = vowels.index(letter)
    next_vowel = vowels[current_id + 1]
    string += next_vowel
    index += 1
  end
  string
end

When I pass "aeiou" as a parameter to my method, it just takes "a", and prints "eeeee".

vowel("aeiou") # => "eeeee"

What is your question?

sawa
– sawa

2016-04-03 07:12:34 +00:00
Commented Apr 3, 2016 at 7:12 — sawa
– sawa, Commented Apr 3, 2016 at 7:12

Aleksei Matiushkin · Accepted Answer · 2016-04-03 06:59:29Z

2

You are always appending the vowel, found by index current_id = vowels.index(letter) (increased by one.) That’s why the code appends e (the next to a) five times. index variable is used as a loop counter only.

There is another glitch with this code: when letter is the last one, current_id is an index of the last letter and vowels[current_id + 1] is nil.

At the moment I am unable to provide a solution for this problem, because the description and expected result are not consistent: “moving every letter forward” won’t produce "eioua" on the given input.

answered Apr 3, 2016 at 6:59

Aleksei Matiushkin

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2 Comments

Danny Rosenfeld Over a year ago

Ah, sorry I didn't mean one letter forward- I meant that each vowel would become the next vowel to the right of it so "a" would become "e" and "u" would become "a." I also noticed that vowels[current_id + 1] becomes nil but I still don't fully understand why can you elaborate? Thank you for the helpful feedback!

Aleksei Matiushkin Over a year ago

When current_id is an index of the last letter, current_id + 1 is an index that is greater than string length, that said, it’s an non-existing index. 'abc'[3] is e.g. nil.

Cary Swoveland · Accepted Answer · 2016-04-03 15:14:58Z

1

If you want to rotate the letters of the word (and form a new word, as opposed to modifying the word in place) one way is:

str = "aeiou"

new_str = str.chars.rotate.join.   #=> "eioua" 
str                                #=> "aeiou"

If you wish to modify the string in place:

str.object_id.                     #=> 70128532752540 
str.replace(str.chars.rotate.join) #=> "eioua"
str                                #=> "eioua" 
str.object_id                      #=> 70128532752540

edited Apr 3, 2016 at 15:14

answered Apr 3, 2016 at 8:06

Cary Swoveland

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1 Comment

tadman Over a year ago

This is a much better way of doing it. Ruby has all these short Enumerator based methods that are really great when they can be used in conjunction.

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