class String

str.first(6) #=> "hello"
str.first(0) #=> ""
str.first(2) #=> "he"
str.first(1) #=> "h"
str.first #=> "h"
str = "hello"

given limit is greater than or equal to the string length, returns self.
from the beginning of the string until it reaches the limit value. If the
Returns the first character. If a limit is supplied, returns a substring

def first(limit = 1)
  if limit == 0
    ''
  elsif limit >= size
    self
  else
    to(limit - 1)
  end
end