CODEWITHSUNDEEP
ruby
sivabudh
sivabudh

Reputation: 32645

Doesn't Ruby have isalpha?

Like Python? I'm trying to check whether each character in a string is an alphanumeric or not?

Upvotes: 17

Views: 17983

Answers (5)

Rodrigo Dinamarca
Rodrigo Dinamarca

Reputation: 1

there's an easy way to do it:

def isalpha(cstring) # Return true if cstring is a text
    if cstring.to_i == 0 && cstring != "0"
        lret = true
    else
        lret = false
    end
end

def isnum(cstring) # Return true if cstring is a number
    if cstring.to_i == 0 && cstring != "0"
        lret = false
    else
        lret = true
    end
end

Upvotes: 0

sixty4bit
sixty4bit

Reputation: 7956

Here's a way to do it without regex if you have trouble remembering regex (like me!):

def alpha?(char)
  char.upcase != char.downcase
end

For any other character than a letter, #upcase and #downcase work but have no effect, so we can assert that the char's upcase and downcase values are not equal to determine that it's a letter.

Upvotes: 4

steenslag
steenslag

Reputation: 80075

The python function only works for ASCII chars; the [[:alnum]] regex would do things like "tëst".alpha? => true. match/\w/ matches underscores, so that leaves

def isalpha(str)
  return false if str.empty?
  !str.match(/[^A-Za-z]/)
end

to reproduce the Python behaviour.

Upvotes: 5

Sergio Tulentsev
Sergio Tulentsev

Reputation: 230461

You can roll your own :) Replace alnum with alpha if you want to match only letters, without numbers.

class String
  def alpha?
    !!match(/^[[:alnum:]]+$/)
  end
end

'asdf234'.alpha? # => true
'asdf@#$'.alpha? # => false

Upvotes: 20

tadman
tadman

Reputation: 211670

There's a special character class for this:

char.match(/^[[:alpha:]]$/)

That should match a single alphabetic character. It also seems to work for UTF-8.

To test a whole string:

string.match(/^[[:alpha:]]+$/)

Keep in mind this doesn't account for spaces or punctuation.

Upvotes: 28

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