added tested input ranges to description ( also fixed "acceps", and did minor cleanup and language-agnosticism. hope that's OK ).

Seems to be correct in C. I'll close the issue. The mentioning op input range could become a suggestion instead.

Must be C that doesn't. The Python original does ( in random tests only ), and JS, Haskell and LC all do.

0 is obviously a valid input.

Sometimes it's not entirely clear. Maybe draw a primitive view layout

"Should return null for invalid arguments" The last check yields a number, but should return null. I used the isNaN method, but it doesn't work. Are you using standard primitive data in your test?

Nice Kata!

Stupid task: a vague theory that is misleading

nice solution, i like it

this task does not correspond to the seventh level of difficulty

You should complete that in order to accept arguments like shown in the example.

Your task is to write a function, smartSum, that returns the sum of an arbitrary number of arguments.

There are no incoming arguments. How to write a function?

This is nice Kata! :=)

OMG. It was so easy.....I wrote 50 lines of code