Re: map (associative array) loses values?

From:
Pete Becker <pete@versatilecoding.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 11 Sep 2007 11:47:36 -0400
Message-ID:
<2007091111473616807-pete@versatilecodingcom>
On 2007-09-11 11:42:18 -0400, jeroenvlek@gmail.com said:

Hi there,

I've never done this before, so I don't know about any layout
possibilities. My apologies :)

The problem is this:

I've written a function:

map<const char*, int> *SearchText::countWords()
{
    map<const char*, int> *table = new map<const char*, int>;


There's no reason to create this map on the heap. Make it a local

    (*table)["aap"] = 1;
    (*table)["noot"] = 2;

    cout << (*table)["aap"] << endl;
    cout << (*table)["noot"] << endl;

    return table;
}

Which I want to use like this:

try {
    SearchText *text = new SearchText("test.txt");
    map<const char*, int> *table = text->countWords();
    cout << (*table)["aap"] << endl;
    cout << (*table)["noot"] << endl;
}
catch(int ex) {
    cout << "Could not open file." << endl;
}

However, I get the following output:

1
2
0
0

Meaning that the first two output statements (in the function itself)
do their job and the second two do not.

I guess it's some sort of allocation problem, but what could I do
different? I guess I could use maybe malloc or calloc, but shouldn't
this be also possible with new?

BTW making table static in the function didn't help.


--
  Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

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