On 02/15/2021 06:47 PM, Chris Angelico wrote:
On Tue, Feb 16, 2021 at 8:44 AM Mark Filipak (ffmpeg)
<[email protected]> wrote:
On 02/15/2021 04:32 PM, Carl Zwanzig wrote:
On 2/15/2021 1:26 PM, Mark Filipak (ffmpeg) wrote:
Yes, I'm aware of C++. It's sort of a 'C' language architecture hack, isn't it?
More like butchery ...
Ooooo... that's harsh. :-)
Glad it's making more sense now.
z!
Thanks for the confirmation. Now, regarding pointers-to-pointers and '*' as a
unary operator.....
A pointer, at its core, is a number representing a place in memory. A
pointer to a pointer is a number representing the place in memory
where you can find another number that'll tell you where you want to
go. You want to know where the Sword Master can be found, but I won't
tell you where he is; all I'll tell you is that the shopkeeper knows
where to find the Sword Master. I point you to the shopkeeper, and
then you ask him to point you to the Sword Master.
The asterisk, as a unary operator, is one step in that process.
Something like this:
int **trial = find_sword_master();
Oops, I'm getting lost in the story of the Sword Master. You're describing indirection. I have no
problem with indirection. The problem I have is simply with syntax interpretation because to me,
every variable (or constant) in every language is a location in memory, so when you write that a
number represents a place in memory, to me it's undistinguished, it's not any different than any
other variable (in any location in memory).
Does '*' (a unary operator) that precedes a variable's name indicate that the named variable is a
pointer? Or do I have that bit wrong?
Is '**' also a unary operator? Or is it 2 unary operators, '*'+'*'? I suspect that '**' is the
infamous pointer-to-pointer (i.e. doubly indirect), or do I have that bit wrong?
"trial" is a number that says where in memory the shopkeeper is.
What's that number?
printf("Shopkeeper is at %p\n", trial);
I have no idea what '%p' means or what you're trying to demonstrate by the code. I don't know why
the printf has a 2nd arg: 'trial'. '%' is modulo, but modulo is a binary operator, not a unary
operator. That it's in a string just adds to the mystery.
"*trial" is the number that can be found there. What's that number?
printf("Sword Master is at %p\n", *trial);
Okay, now I'm lost. is 'trial' a variable or a pointer? Specifically, is '*trial' a pointer that's
labeled "trial" or is it a pointer to a variable that's labeled "trial"? Or are both labeled
"trial"? Or does the string "*trial" just represent an entity that's just a relative memory address
that neither the compiler nor the runtime system normally discloses? If your 'printf' functions
print, what do they print? ...Yes, I know that 'print' doesn't mean print on a printer. The only
thing I can guess is that "%p" is some sort of token, but I don't know its meaning.
The rest of 'C' syntax, and precedent, and operators, etc. I know. It's just pointers that mystify
me. Now I understand what a struct actually is but pointers?... not so much. I thought I understood,
but '**' fuddled it. I'm afraid I'm one of the people who, for example, actually prefer BNF to
textual descriptions.
--
Any journey, no matter how long, is just a series of small steps.
"Government is the problem!" -- 1982 and onward.
"_______ is the enemy of the people!" -- 2016 and onward.
"You have to fight like hell or you're not going to have a country!" -- Jan 6,
2021.
It isn't the distance that's important, it's the direction.
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