Does it cause any problems beyond that? For example, does it interfere with some elegant patterns, or result in some bug prone code, etc?

FWIW, the single main annoyance I've had with python was its treatment of strings as iterables of single character strings. While not wrong in any obvious theoretical sense, it conflicts with the mental model of many developers (both new and experienced) and has probably caused more bugs than any other feature of Python (and even more ugly type checks to avoid such bugs). When people realized it was a problem and discussed removing this feature, Guido said he had tried but (a) it was too much work and (b) he felt the benefits are too great to give up (https://mail.python.org/pipermail/python-3000/2006-April/000...).

I'm confused mainly because a person with a mathematical background created a language with such an obvious blunder. When I have to use the language (and I do often) I am not confused about string concatenation, I am ashamed of having to use this ridiculous notation.

s[0] == s[0][0][0][0]

While it makes sense to think of them as sequences, this has bitten me more than I care to admit. OT: Is there a name for things we love to complain about, but wouldn't change?

Also, to the best of my knowledge there is no place in the bible of maths that defines + to be commutative. In particular, addition of (infinite) ordinals is not commutative.

Yes, wedge product[0], written as tilde (~)[1]:

  "a"~("b"~"c") = "abc" = ("a"~"b")~"c" # associative
  "a"~"a"~"a" = "aaa" = "a"^3 # exponentiates with repeat
  -"abc" = "cba" # (with - as string reverse)
  "ab"~"cd" = -(-"cd" ~ -"ab") # weakly[2] anticommutative

0: https://en.wikipedia.org/wiki/Wedge_product

1: Not caret (^), because that makes a good exponentiate operator.

  2: # vector wedge product is strongly anticommutative
  u~v = -(v~u) = -(-v~-u) # with vector negation

Literally, any other operator would be better than addition. A space, a dot, a product, two dots, a minus sign, whatever. Anything except the visually commutative plus.

> Because I feel that using a less common one would harm beginner-friendliness significantly.

Usage of + for string concatenation is fairly new, probably invented by C++ (which, by the way, uses bit shift operators for output, so it is not really an example of sane language).

  "A"+"B" = Regex("A|B") = Regex("[AB]") # or maybe
  "A"+"B" !> [?]Error: cannot convert /A|B/ to type str
  "A"*6 !> TypeError: <str> * <int>

Actually, given that concatenating sequences (strings are an example) is a fairly common operation and for some kinds of sequences, so is adding them elementwise, it would be better not to use a common mathematical operator for concatenation, but to give it its own.

Some of you guys have really wicked minds.

IMO it weirds people out

I'm asking partly because Ocaml uses stardot for floating point multiplication.

"a" * "b" == "ab"

"a" ^ 3 == "aaa"

Though the dot version is actually almost possible because of a special syntax in Julia called broadcasting, which applies any function element-wise.

"a" .* ["a", "b", "c"] == ["aa", "ab", "ac"]

["a", "b", "c"] .* "a" == ["aa", "ba", "ca"]

("a" * ["a", "b", "c"] would raise an error)

A much saner choice. I would prefer a space, still.