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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: double free
Date: Wed, 13 Jul 2016 13:24:53 -0700
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BartC <bc@freeuk.com> writes:
> On 13/07/2016 20:15, Ben Bacarisse wrote:
>> BartC <bc@freeuk.com> writes:
>> <snip>
>>> ** has a long history of being used for exponentiation in programming
>>> languages (notably in Fortran).
>>>
>>> But apart from not meaning a power operation in C, it's a little odd
>>> that the * after A means one thing, and the * before B means another.
>>>
>>> (C is far from alone in allowing confusing combinations of
>>> operators. In Python, ++A is quite legal, but it doesn't mean what it
>>> does in C! It means +(+A). But at least each + means exactly the same
>>> as the other. And Python uses ** to mean pow().)
>>
>> Many allow you to write A--B.  The usual advise is better layout (and
>> some might even advocate parentheses) not that the language be
>> re-designed.
>
> Overloading "-" to mean both unary negate and binary minus is well known 
> from school arithmetic. It's less of a surprise. Until a language uses 
> "--" to have a third meaning (eg. decrement in C or pointer subtract in 
> one my old languages).

In some languages "--" introduces an end-of-line comment.

> I would anyway use brackets around -B if "-" was adjacent to another 
> operator. If I was in a hurry, I'd use a space.

I'd use `A + B` rather than `A--B` (unless I had some specific
reason to negate B and subtract the result from A, but then I'd
probably have a comment explaining it).  And yes, I'd write
`A - -B`, or *maybe* `A - (-B)`.

Just curious, how long do you think it's going to take you to get over
your surprise that `*` has multiple meanings?

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"