ruby - how to pad "groups of 5 characters" with undersores in last group?

Question

I want my string in groups of 5 characters, .e.g.

thisisastring => ["thisi", "satri", "ng"]

but I also want the last group to be padded with __'s, e.g.

thisisastring => ["thisi", "satri", "ng___"]

I have got as far as the string splitting:

"thisisastring".scan /.{5}/)

["thisi", "satri", "ng"]

but not too sure how to do the padding for that last group to make it "ng___"

although starting to think that combinations of dividend (div()), modulus (%) and .ljust might do it.

Maybe number of padding characters would be: (length % 5) * "_" (if you can multiply that) ?

Perhaps something that uses:

ruby-1.9.2-p290 :023 > (len % 5).to_i.times { print '_' }
___ => 3

Not a Ruby expert, but why not just check the last element in the array for its length. Append 5-length '_'s to it? — , Feb 02 '12 at 21:37

score 6 · Answer 1 · answered Feb 02 '12 at 21:35

6

Not even close to efficient, but if you wanted t to one-line it, something like this should work:

"thisisastring".scan(/.{1,5}/).collect {|x| x.ljust(5,"_")}

answered Feb 02 '12 at 21:35

J. Holmes

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I like it. When you say not close to efficient it would probably be better than using activesupport, no? – Michael Durrant Feb 02 '12 at 22:02
I can do timing runs but wanted opinion too – Michael Durrant Feb 02 '12 at 22:02
1

it runs `ljust` on every item in the enumeration, when really the last item is the only one that is ever less than 5 characters long. – J. Holmes Feb 02 '12 at 22:04

score 4 · Accepted Answer · answered Feb 02 '12 at 22:14

4

Since the adjustment is only required on the last element, it is more effective to do the adjustment before splitting rather than itterating over the elements to do adjustment.

("thisisastring"+"_"*("thisisastring".length % 5)).scan(/.{5}/)

answered Feb 02 '12 at 22:14

sawa

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ruby - how to pad "groups of 5 characters" with undersores in last group?

2 Answers2