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From: Bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: Top 10 most common hard skills listed on resumes...
Date: Tue, 10 Sep 2024 01:20:08 +0100
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On 10/09/2024 00:53, Keith Thompson wrote:
> Bart <bc@freeuk.com> writes:
>> On 08/09/2024 17:44, Bart wrote:
>>> On 08/09/2024 16:39, Ben Bacarisse wrote:
>>>> Bart <bc@freeuk.com> writes:
>>>>
>>>>> In language like C, the LHS of an assignment is one of four categories:
>>>>>
>>>>>     A = Y;         // name
>>>>>     *X = Y;        // pointer
>>>>>     X[i] = Y;      // index
>>>>>     X.m = Y;       // member select
>>>>
>>>> I can think of three others.  There may be more.
>>> OK, so what are they?
>>
>> TM:
>>> Yes, very good.  I count four or five, depending on what
>> differences count as different.
>>
>> I guess nobody is going to say what those extra categories are, are they?
> 
> The LHS of an assignment must be a modifiable lvalue.  Searching for the
> word "lvalue" in the standard's section on expressions yields several
> forms not listed above:
> 
> - A parenthesized lvalue:
>    (A) = Y;
> 
> - A generic selection whose result expression is an lvalue:
>    _Generic(0, int: A) = Y;
>    Not sure why you'd do this.
> 
> - X->m, where X is a pointer (you might think of that as the same
>    category as X.m, but the standard doesn't define the -> operator in
>    terms of the . operator)
> 
> - A compound literal:
>    int n;
>    (int){n} = 42;
> 
>    This assigns a value to a temporary object which is immediately
>    discarded.  I can't think of a valid use for this.
> 

OK, thanks for the prompt response.

You listed 4 examples; the 4th one I had no idea about (I don't support 
compound literals anyway).

The first 3, I have doubts as to whether they warrant their own categories.

The first two just end up doing an assignment to A (parentheses are 
no-ops in terms like these anyway).

While the X->m term is exactly equivalent to (*X).m. I put these three 
through my compiler and they produced the same AST as A = Y or *(X).m.

So I might call them curiosities rather than practical categories that 
offer new possibilities.

For example, one of mine (I have several more actual ones) is multiple 
assignment: (a, b) = (c, d).