Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Useless expressions [was Re: Undefined behaviour in C]
Date: Mon, 28 Mar 2016 14:29:41 +1100
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On Mon, Mar 28, 2016 at 1:59 PM, Tim Chase
<python.list@tim.thechases.com> wrote:
> On 2016-03-28 12:38, Chris Angelico wrote:
>> 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.
>
> Is it only the "*add* two things" or are you decrying any generic
> operator that gets evaluated and then drops the result?
>
> Steven recently opened a thread ["Bash-like pipes in Python"] where
> this exact sort of thing would be done:
>
>   get_values() | filter("smith") | sort("income") | send_to_printer()
>
> Several different solutions were posited with varying degrees of
> conciseness-vs-pythonicity-vs-pipe'ness.

I was talking about any operator that, for built-in types, does no
mutation and has no effect aside from its return value. So yes, the
use of the pipe is a perfect counter-example - or rather, proof that
my concern is a code smell rather than fundamentally bad. C++ started
it with the iostream << and >> overloads; personally, I think that's
more cute than useful, but there are times when it can be extremely
useful.

So I revise my stance: A DSL that requires you to do this *may be*
poorly designed, and needs a very solid justification.

> That said, I'm in the "let the compiler accept valid syntax; leave it
> to the linter" camp.

Yeah definitely.

ChrisA