Useless expressions [was Re: Undefined behaviour in C]

[Chris Angelico]

On Mon, Mar 28, 2016 at 12:24 PM, Steven D'Aprano <steve at pearwood.info> wrote:
>>
>>    f()         # Probably OK
>>    g()         # Probably OK
>>    f()+g()     # Probably not OK
>
> You don't and can't know what's "probably not" okay unless you know what
> type of object both f and g return.
>
> Don't think about floats and ints and strings. Think of complex objects with
> operator overloading. You're probably thinking of `x + y`. Instead, think
> of things like:
>
> graph + node
> database + table
>
> in a procedural style instead of a functional style. With operator
> overloading, we have the ability to write domain-specific little languages.

I would still look askance at code that adds two things and drops the
result, though. The compiler can't discard it, but if a linter
complains, I'd support that. A DSL that requires you to do this is,
imo, poorly designed. It'll make every subsequent maintainer wonder if
the code is buggy or not.

But it's still...

> ... not the compiler's job to cast value judgements on what is good or
> likely style, it must accept anything legal. If you want something to make
> value judgements about style, or get warnings about what looks like legal
> code but might be an error, then you should use a linter like PyChecker,
> Pylint, Jedi or similar. That's not the compiler's job.

Exactly.

ChrisA