Re: Work with Arrays

From:
"Eric.Malenfant@gmail.com" <Eric.Malenfant@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 30 Apr 2008 07:15:52 -0700 (PDT)
Message-ID:
<b2a1dafb-6205-463a-b6dd-819fcde52e5a@b1g2000hsg.googlegroups.com>
On Apr 30, 9:56 am, Frank Liebelt <ecos...@hotmail.com> wrote:

Hi


Hi Frank,

I hope my english ist good enough to explain what my problem is.


I hope mine is good enough to answer :-)

I want to create a array with two dimensions. Each index should have a
second dimension with three indexes.
Like: myarr[0][0-2] , myarr[1][0-2] and so on...

The size of the first dimension is unknown the second ist allways three.


[snip]

Within the headerfile i wrote: vector<char> arrSpec;

[snip]

Now the Problem.
-> arrSpec[listPos].resize(3);
Wont work. I got the following compiler error:


The return type of operator[] is the vector's element type which is,
in the present case, "char". "char" does not have a "resize" member
function.

The next three line have this compiler error:
invalid types `char[int]' for array subscript


And "char" has no operator[] either.

What you're trying to achieve is not entirely clear to me, but do you
really need to access the sub-elements with this double indexing
scheme? Looking at your code below, it seems that sub-index 0 is
always "id", 1 is "name" and 2 is "path". So, for example, to get the
name of the n-th element, would'nt this:
  arrSpec[n].name
be more expressive than:
  arrSpec[n][1]
?

If yes, then a solution could be: create a type for your elements,
say:
  struct Element
  {
    char* id;
    char* name;
    char* path;
  };
and store you data in a vector<Element>

If you really need to use a double-indexing scheme, you could use
boost::array, and define your vector as:
std::vector<boost::array<char*, 3> >

HTH,

=C9ric Malenfant

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