Get remaing characters in a string

ruby-talk
1

Hi.

I need to get the last three characters in a string. I couldn't find a
function in the String class so I came up with this:

class Remainder

attr_writer :n

def initialize(t = "", n = 0)
   @t = t.to_s
   @n = n.to_i
end

def get
   get_remaining_letters
end

private
def get_remaining_letters
   s = @t.size
   if s < @n
     r = 0
   else
     r = s - @n
   end

   ft = @t.slice(r, @n)
end

end

t = Remainder.new("Guttesen", 5)
puts t.get
tesen
t.n = 4
puts t.get
esen

Did I reinvent the wheel or does it make sense to add it to String?

regards
Claus

2

I'd just do str.slice!(-n .. -1) instead:

str = "Hello World"
str.slice!(-3 .. -1) # => "rld"
str # => "Hello Wo"
str.slice!(-1 .. -1) # => "o"
str # => "Hello W"

···

On 2007-01-07 01:21:54 +0100, "Claus Guttesen" <kometen@gmail.com> said:

Hi.

I need to get the last three characters in a string. I couldn't find a
function in the String class so I came up with this:

Did I reinvent the wheel or does it make sense to add it to String?

3

You can use String# with a Range instead:
>> "asdfhsdfabc"[-3..-1]
=> "abc"

or you can specify the length:
>> "asdfhsdfabc"[-3, 3]
=> "abc"

Negative numbers count from the end of the string. So basically the strings length plus your negative number is the position from the start of the string.

Dan

Claus Guttesen wrote:

···

Hi.

I need to get the last three characters in a string. I couldn't find a
function in the String class so I came up with this:

class Remainder

attr_writer :n

def initialize(t = "", n = 0)
  @t = t.to_s
  @n = n.to_i
end

def get
  get_remaining_letters
end

private
def get_remaining_letters
  s = @t.size
  if s < @n
    r = 0
  else
    r = s - @n
  end

  ft = @t.slice(r, @n)
end

end

t = Remainder.new("Guttesen", 5)
puts t.get
tesen
t.n = 4
puts t.get
esen

Did I reinvent the wheel or does it make sense to add it to String?

regards
Claus

4

You can index strings from the right with negative numbers:

   "abcdef"[-3..-1] => "def"

I think that might be all you need.

David

···

On Sun, 7 Jan 2007, Claus Guttesen wrote:

Hi.

I need to get the last three characters in a string. I couldn't find a
function in the String class so I came up with this:

class Remainder

attr_writer :n

def initialize(t = "", n = 0)
@t = t.to_s
@n = n.to_i
end

def get
get_remaining_letters
end

private
def get_remaining_letters
s = @t.size
if s < @n
   r = 0
else
   r = s - @n
end

ft = @t.slice(r, @n)
end

end

t = Remainder.new("Guttesen", 5)
puts t.get
tesen
t.n = 4
puts t.get
esen

Did I reinvent the wheel or does it make sense to add it to String?

--
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A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black\)
    (See what readers are saying! http://www.rubypal.com/r4rrevs.pdf\)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

5

Claus Guttesen wrote:

Hi.

I need to get the last three characters in a string. I couldn't find a
function in the String class so I came up with this:

class Remainder

attr_writer :n

def initialize(t = "", n = 0)
   @t = t.to_s
   @n = n.to_i
end

def get
   get_remaining_letters
end

private
def get_remaining_letters
   s = @t.size
   if s < @n
     r = 0
   else
     r = s - @n
   end

   ft = @t.slice(r, @n)
end

end

t = Remainder.new("Guttesen", 5)
puts t.get
tesen
t.n = 4
puts t.get
esen

Did I reinvent the wheel or does it make sense to add it to String?

regards
Claus

If the length of the string is less than 3,
the entire string will be returned.

s = "ab"
s[ /.{0,3}$/ ]
s[-3,3] || s

6

> I need to get the last three characters in a string. I couldn't find a
> function in the String class so I came up with this:
>
You can index strings from the right with negative numbers:

   "abcdef"[-3..-1] => "def"

I think that might be all you need.

I see. Thank you very much for all the replies.

regards
Claus