CODEWITHSUNDEEP
ruby
mjekov
mjekov

Reputation: 682

Finding exact number of a given symbol at the beginning of a string

I'm trying to solve a Ruby problem using as less code as possible :). I want to check if a given string starts with a varying number of symbols, lets say between one and three 'a'. That's easy using reg exp, I can write string.match(\^a{1,3}.*\). But then I have to make changes on the string depending of the exact number of a's. How can I detect them without using three if's like that:

do_string_manipulation1 if string.match(/^a.*/)
do_string_manupulation2 if string.match(/^aa.*/)
...

Thanks in advance :)

Upvotes: 0

Views: 51

Answers (2)

Gazler
Gazler

Reputation: 84140

Depends on what your string manipulations are.

You can determine the number of consecutive a's by doing:

string.match(/^(a{1,3}).*/)[1].size

You haven't defined the rules, so mine are:

"a"   - downcase
"aa"  - reverse
"aaa" - swapcase

So my code is:

string.send([:downcase, :reverse, :swapcase][string.match(/^(a{1,3}).*/)[1].size-1])

If your rules are more complicated, then you can define them as methods on a class and call them depending on the number returned.

Upvotes: 1

Dominik Honnef
Dominik Honnef

Reputation: 18430

Why not use a modified version of the first regexp and then simply count the a's it returns? A la

m = string.match(/^(a{1,3})/)
case m[1].size
  when 1
  when 2
  when 3
end

Of course you can also use an array to store routines to call, depending on the number:

routines = [nil, method(:do_string_manipulation1), method(:do_string_manipulation2), ...]
routines[m[1].size].call

Upvotes: 1

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