I have written a .

And, there are some points to ask

• What is the appropriate behavior when calling concat/prepend without argument?

• The code attached now returns just self

• What should happen when writing ar.concat(ar, ar)?

• ar = [1]; ar.concat(ar, ar) #=> [1,1,1]? or [1,1,1,1]?

• ar << ar << ar returns [1,1,1,1], of course because this is just a sequence of binary operations

• However, I feel "ar.concat(ar, ar)" saying "append present content of the array twice to the array", meaning [1,1,1]

• The code attached returns [1,1,1,1], for now, just for the simplicity of implementation

I wrote another refined for a problem stated in a previous post.

It behaves like below

ar = [1]
ar.concat(ar, ar) #=> [1,1,1]

str = "ab"
str.concat(str, str) #=> "ababab"

I added some test cases for Array#concat, String#concat and String#prepend and refined error handling.
Also, I fixed my code to conform to convention.
Any feedback is welcome!

Applied in changeset r56021.

multiple arguments

• array.c (rb_ary_concat_multi): take multiple arguments. based
  on the by Satoru Horie. [Feature ]
• string.c (rb_str_concat_multi, rb_str_prepend_multi): ditto.