Feature #12333: `String#concat`, `Array#concat`, `String#prepend` to take multiple arguments

• Status: Closed
• Assignee: -
• Target version: -

[sawa (Tsuyoshi Sawada)]

I would like String#concat, Array#concat, String#prepend to take multiple arguments

s = ""
s.concat("a", "b", "c")
a.prepend("A", "B", "C")
s # => "ABCabc"

a = []
a.concat(["a"], ["b", "c"])
a # => ["a", "b", "c"]

[duerst (Martin Dürst)]

I think this can occasionally be helpful, and shouldn't be too difficult to implement. Can you provide a patch?

[spinute (Satoru Horie)]

I will try to write a patch for it!

[spinute (Satoru Horie)]

• File multi_concat_prepend.patch multi_concat_prepend.patch added

I have written a patch.

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

[spinute (Satoru Horie)]

• File fixed_multi_concat_prepend.patch fixed_multi_concat_prepend.patch added

I wrote another patch 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"

[sawa (Tsuyoshi Sawada)]

Satoru, thank you for the patch.

And you are making good points with the questions you raised.

• What is the appropriate behavior when calling concat/prepend without argument?
• The code attached now returns just self

I agree with this behavior. I think this would be the most natural.

• 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

This is more logical (in some sense), but counter-intuitive.

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

This is more intuitive, but may be less logical.

I have preference with the second option, but am not completely sure. Maybe other people might have different opinions.

[hsbt (Hiroshi SHIBATA)]

• Related to Feature #12247: accept multiple arguments at Array#delete added

[matz (Yukihiro Matsumoto)]

Approved. I want to

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

to result [1,1,1].

Matz.

[spinute (Satoru Horie)]

• File multi_concat_prepend.patch multi_concat_prepend.patch added

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!

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset r56021.

---

multiple arguments

• array.c (rb_ary_concat_multi): take multiple arguments. based
  on the patch by Satoru Horie. [Feature #12333]
• string.c (rb_str_concat_multi, rb_str_prepend_multi): ditto.

[stomar (Marcus Stollsteimer)]

• Related to Bug #13268: [DOC] Restore docs for String#<< added