Subj : Re: strange string pointer to strings...?
To   : borland.public.cpp.borlandcpp
From : maeder
Date : Thu Sep 29 2005 09:36 pm

"mujeebrm" <mujeebrm@y!.com> writes:

> i am not in a school. I am learning to program as a hobby thru
> c,c++. this is not a school assignment.

Please note that there is no programming language called "C,C++". C
and C++ have become quite distinct languages, each with its own
idioms, best (and worst) practices etc.

Others may disagree here, but I think that you should either learn C
or C++, but not both at the same time.

Whichever you pick, make sure to have a look at the book reviews at
http://www.accu.org/ .


> this program is taken from example code given in a book which i
> could not understand and sought U peoples help in deciphering this
> code.

Good. No program is bad enough to not work as a bad example. :-)


> #include <stdio.h>
> #include <conio.h>
> #include <string.h>

Since you are learning, please note that <conio.h> (and the getch()
function probably declared in it) aren't part of the C nor the C++ ISO
Standard. I personally think that you would do better with a book that
sticks to the language standard.


> int main(void)
> {
>
> /* this does not make sense to me that when i keep adding rows and columns
>    of strings to this array of pointers to strings it just keeps
>    going on, any explanation for this ?
> */
> char *s[][5]= {
> "one","qwer",
> "two", "rewq",
> "three", "qwer",
> "four", "rewq",
> "five", "qwertttt",
> " ", " "
> };

Yesterday, it didn't make sense to me either :-) My remark about 5
being too small was wrong.

It's a complex statement, defining a complex data structure and
initializing it in a rather obfuscated way.

First, you have to learn how to read declarators. The right way to
read them is to start at the name being declared (which isn't always
as obvious as here) and read outward, following operator
precedence. In this case, this means:

s is defined to be an array of a size determined by the initializer
which is part of the definition. The elements of s are arrays of 5
pointers to char.

The initializer is the part of the definition surrounded by curly
braces. In this particular case, s[0][0] is initialized with "one",
s[0][1] with "qwer" etc. s[0][4] is initialized with "three", s[1][0]
with "qwer" and so on. Since there are twelve string literals in the
initializer, the second " " initializes s[2][1]. s has thus 2
elements, and the remaining elements of s[2] are initialized to be
null pointers.

Please do look up declarators and initializers in a good text
book. This part of the C syntax is generally considered an experiment
that failed.

And let me repeat that it's a really bad idea to have a pointer to
non-const (such as s[0][0] point at a string literal). The type of s
should be

char const *s[2][5]


> char **sp=0,w[10];
> int c;

Having read the above-mentioned textbook chapters, what do these
statements mean?

Going on doesn't make any sense before you can answer this question.

.