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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: relearning C: why does an in-place change to a char* segfault?
Date: Sat, 28 Sep 2024 13:42:31 -0700
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Phillip Frabott <nntp@fulltermprivacy.com> writes:
> In reply to "Janis Papanagnou" who wrote the following:
[...]
>> I also think (for various reasons) that "constants" is not a good
>> term. (Personally I like terms like the Algol 68 term, that seems
>> to "operate" on another [more conceptual] abstraction level.)
>> 
>> But you'll certainly have to expect a lot of anger if the terminology
>> of some standards documents get changed from one version to another.
>
> The only gripe I would have if we synonymized constants and literals
> is that not every const is initialized with a literal. There have been
> times where I have initialized a const from the value of a variable. I
> don't think that const and literals are the same thing because of
> this.

Though the word "const" is obviously derived from the English word
"constant", in C "const" and "constant" are very different things.

The "const" keyword really means "read-only" (and perhaps would have
been clearer if it had been spelled "readonly").

A "constant" is what some languages call a "literal", and a "constant
expression" is an expression that can be evaluated at compile time.

For example, this:

    const int r = rand();

is perfectly valid.

Incidentally, the N3301 draft of the C2Y standard has this change
applied to it:

    Syntax
        constant:
            integer-literal
            floating-literal
            enumeration-constant
            character-literal
            predefined-constant

The predefined constants are false, true, and nullptr.

(I find it a bit odd that enumeration and predefined constants are still
called constants, not literals.)

Compare C17:

    Syntax
        constant:
            integer-constant
            floating-constant
            enumeration-constant
            character-constant


https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3301.pdf
(open-std.org seems to be down at the moment.)

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */