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Rick Rajter · Guest

Hi everyone. Minimal background info, then my problem/question

I am trying to relearn/increase my knowledge of C++ for some upcoming
projects that I will need to do for grad school. I read through the
oreilly "practical c++ programming book". Decent, though they tend to
spend a lot of time with the theory of coding (which is not to say
that this information isn't important). Anyway, the one part of the
book that really stumped me was the array of pointers. The example
just confused the heck out of me, and upon coding up a quick and dirty
c++ file, i'm tending to believe that it's incorrect (or at least
specific to structs)...

Here's the code.

// Pointer to the data
struct mailing *list_ptrs[MAX_ENTRIES];
int current; // Current mailing list entry

// ....
for (current = 0; current = number_of_entries; ++current) {
list_ptrs = &list[current];
++list_ptrs;
}
// Sort list_ptrs by zip code

basically, this is just a skeleton saying that we want to get an array
of pointers to all of the structs from the array of structs called
list

My question.

the line "list_ptrs = &list[current]", should their not be a similar
index on list_ptrs? I am under the impression (perhaps wrongly so)
that list_ptr is the address of the 0 position of the list_ptr array.
When in fact, we want to assign the "list" address of index "current"
to the pointer in array "list_ptr" of index "current". And the
incrementer at the end definitely stumps me. Why would you want to
move the 0 position of the array? wouldn't it then be impossible (or
at least annoying to do a *(list_ptr-index)) to access the pointer
data that one just stored?

I wrote a quick and dirty script (granted, using int arrays instead of
struct arrays)

#include<iostream>

int main()
{
const int COUNT=6;
int i=0;
int array[COUNT] = {1,4,6,8,9,13};
int *array_ptr[COUNT];
for(i=0;i {
array_ptr[i]=&array[i];
}
std::cout<<" "< }

And I was able to get 13 13 for output, which is the way I expected
it.

Trying to compile how the book states, I get compile errors.

So final question, is the book correct but just in a different way?
Or is their syntax old, or for classes/structs. I've been running
this through my head for a while, and can't seem to feel satisfied
that the first way listed could be a good way to do it.

Thanks in advance to any help

-rick

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David Fisher · Guest

"Rick Rajter" asked:

Paul · Guest

Could we see some pertinent compile errors?

Also the syntax:

struct struct_name var_name;
for initialization is old C syntax, I believe- I may be wrong here.
Certainly its an uncommon style for modern C++.

-paul

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Francis Glassborow · Guest

In article <5QiJc.19159$%r.203691 (AT) nasal (DOT) pacific.net.au>, David Fisher
<david (AT) hsa (DOT) com.au> writes

Ray Lischner · Guest

On Wednesday 14 July 2004 05:10 pm, Rick Rajter wrote:

llewelly · Guest

[email]rickrajter (AT) mac (DOT) com[/email] (Rick Rajter) writes:

Francis Glassborow · Guest

In article <861xjcjruu.fsf (AT) Zorthluthik (DOT) local.bar>, llewelly
<llewelly.at (AT) xmission (DOT) dot.com> writes

Rick Rajter · Guest

I guess I'm a little dissappointed about this book then, as every
other O'reilly book I have is extremely helpful and fairly error free.

I'll take some of your book recommendations. Thanks for all your help
everyone.

-rick

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