| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"suresh" |
| Date: |
12 Dec 2007 12:24:16 PM |
| Object: |
bogus entries in map (std library) |
Hi,
I am getting zero as value for some keys in my map which can never
happen as per my understanding of my code. These are the details:
I have defined an array of vectors, where each vector element is a
map, like this:
vector<map<string,int> entry>* fulldata ;
using new operator, fulldata is memory allocated and each vector's
size is made 10 by calling resize() function.
The maps are always updated using ++fulldata[i][j][key_string]; This
means that no key_string in the map can have corresponding zero
integer values.
But I get bogus entries in some maps with 0 values corresponding to
some valid key_string.
How can this happen? Interestingly this problem is noticed in the maps
stored in the 2nd position in the vector (for many vectors it is
seen). ie fulldata[i][2][key_string] is zero for many i values.
I am using debian etch with g++ version 4:4.1.1-15.
Thanks for any suggestions,
suresh
.
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| User: "Richard Herring" |
|
| Title: Re: bogus entries in map (std library) |
13 Dec 2007 04:11:47 AM |
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In message
<01d6728f-6232-4e5c-b489-08951c07a6f1@e25g2000prg.googlegroups.com>,
suresh <suresh.amritapuri@gmail.com> writes
Hi,
I am getting zero as value for some keys in my map which can never
happen as per my understanding of my code. These are the details:
I have defined an array of vectors, where each vector element is a
map, like this:
vector<map<string,int> entry>* fulldata ;
using new operator
Why not just use a vector of vectors?
--
Richard Herring
.
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| User: "Mark P" |
|
| Title: Re: bogus entries in map (std library) |
12 Dec 2007 02:56:13 PM |
|
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suresh wrote:
Hi,
I am getting zero as value for some keys in my map which can never
happen as per my understanding of my code. These are the details:
I have defined an array of vectors, where each vector element is a
map, like this:
vector<map<string,int> entry>* fulldata ;
Syntactically invalid statement...
using new operator, fulldata is memory allocated and each vector's
size is made 10 by calling resize() function.
The maps are always updated using ++fulldata[i][j][key_string]; This
means that no key_string in the map can have corresponding zero
integer values.
But I get bogus entries in some maps with 0 values corresponding to
some valid key_string.
How can this happen? Interestingly this problem is noticed in the maps
stored in the 2nd position in the vector (for many vectors it is
seen). ie fulldata[i][2][key_string] is zero for many i values.
I am using debian etch with g++ version 4:4.1.1-15.
Thanks for any suggestions,
suresh
How can we help you if you don't post any code? (Although Victor's
guess is probably a good one given the uselessly little information
you've provided.)
.
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| User: "suresh" |
|
| Title: Re: bogus entries in map (std library) |
12 Dec 2007 11:22:02 PM |
|
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Hi Victor
Thanks for the reply. I read Stroustrup carefully and wrote a small
piece of code to confirm the indexing behaviour. Thanks.
Mark, sorry for the cut paste error in my code. Actually it was
written like this:
typedef map<string,int> entry;
vector<entry>* fulldata ;
Anyway I learned maps better now. Thank you both,
regards
suresh
On Dec 13, 1:56 am, Mark P <use...@fall2005REMOVE.fastmailCAPS.fm>
wrote:
suresh wrote:
Hi,
I am getting zero as value for some keys in my map which can never
happen as per my understanding of my code. These are the details:
I have defined an array of vectors, where each vector element is a
map, like this:
vector<map<string,int> entry>* fulldata ;
Syntactically invalid statement...
using new operator, fulldata is memory allocated and each vector's
size is made 10 by calling resize() function.
The maps are always updated using ++fulldata[i][j][key_string]; This
means that no key_string in the map can have corresponding zero
integer values.
But I get bogus entries in some maps with 0 values corresponding to
some valid key_string.
How can this happen? Interestingly this problem is noticed in the maps
stored in the 2nd position in the vector (for many vectors it is
seen). ie fulldata[i][2][key_string] is zero for many i values.
I am using debian etch with g++ version 4:4.1.1-15.
Thanks for any suggestions,
suresh
How can we help you if you don't post any code? (Although Victor's
guess is probably a good one given the uselessly little information
you've provided.)
.
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|
| User: "Victor Bazarov" |
|
| Title: Re: bogus entries in map (std library) |
12 Dec 2007 12:27:46 PM |
|
|
suresh wrote:
I am getting zero as value for some keys in my map which can never
happen as per my understanding of my code. These are the details:
I have defined an array of vectors, where each vector element is a
map, like this:
vector<map<string,int> entry>* fulldata ;
using new operator, fulldata is memory allocated and each vector's
size is made 10 by calling resize() function.
The maps are always updated using ++fulldata[i][j][key_string]; This
means that no key_string in the map can have corresponding zero
integer values.
But I get bogus entries in some maps with 0 values corresponding to
some valid key_string.
How can this happen? Interestingly this problem is noticed in the maps
stored in the 2nd position in the vector (for many vectors it is
seen). ie fulldata[i][2][key_string] is zero for many i values.
How do you know that there are "bogus entries"? Did you know that
using indexing on a map inserts a default-initialized value into
the map with the key you use do index?
map<int, double> whoa;
if (whoa[42] == 0) {
std::cerr << "BOGUS!!!";
}
Is that what you're doing?
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
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