Hi,
How can I save a reference inside a container?
For example I have:
map<string, unsignedX;
I would like to be able to save a reference to a position inside X.
For a vector, the reference would be the index inside the vector. For
map the reference would be the key (in this case a string). The problem
is that I don't want to store the string as it might be too long. I
would like to have a smaller size reference, like an unsigned or a pointer.
Thanks,
Ray 4 1984
On Feb 23, 11:07 pm, Rares Vernica <rvern...@gmail .comwrote:
Hi,
How can I save a reference inside a container?
For example I have:
map<string, unsignedX;
I would like to be able to save a reference to a position inside X.
For a vector, the reference would be the index inside the vector. For
map the reference would be the key (in this case a string). The problem
is that I don't want to store the string as it might be too long. I
would like to have a smaller size reference, like an unsigned or a pointer.
Thanks,
Ray
hi ray, i'm not so shure i fully understand, but, here it goes :)
i dont know if its possible to have a 'pointer' to inside of a
container ... and even if you could, i think that it would only make
sense for one item of it. if you had more than one, you would have to
find it in a list (or somewhere else and you'd be losing all you
gain).
if the string length is something that bothers into your sistem, you
could try make a hash-table structure.
it takes the best of both worlds. if you could asign an 'unique'
number to each lengthy string, you could use it as the map-key.
yes, this has its own pack of problems (but nothing a list cant fix);
maybe this is too much work if only a couple of keys are length, but
if you can find an easy function string->number its something to
consider.
hope this can help/orient/at-least-not-confuse you =)
Rares Vernica wrote:
Hi,
How can I save a reference inside a container?
For example I have:
map<string, unsignedX;
I would like to be able to save a reference to a position inside X.
For a vector, the reference would be the index inside the vector. For
map the reference would be the key (in this case a string). The problem
is that I don't want to store the string as it might be too long. I
would like to have a smaller size reference, like an unsigned or a pointer.
Thanks,
Ray
Use an iterator, that's what they're for.
typedef map<string, unsignedsu_map;
su_map X;
X["abc"] = 1;
X["def"] = 2;
X["ghj"] = 3;
X["wer"] = 4;
su_map::iterato r i = X.find("def");
i is now a 'reference' to the position of ("def", 2) inside the map.
You really need to read up on iterators in the STL, yu're not going to
get very far without them.
john
John Harrison wrote:
Rares Vernica wrote:
>Hi,
How can I save a reference inside a container?
For example I have: map<string, unsignedX;
I would like to be able to save a reference to a position inside X.
For a vector, the reference would be the index inside the vector. For map the reference would be the key (in this case a string). The problem is that I don't want to store the string as it might be too long. I would like to have a smaller size reference, like an unsigned or a pointer.
Thanks, Ray
Use an iterator, that's what they're for.
typedef map<string, unsignedsu_map;
su_map X;
X["abc"] = 1;
X["def"] = 2;
X["ghj"] = 3;
X["wer"] = 4;
su_map::iterato r i = X.find("def");
i is now a 'reference' to the position of ("def", 2) inside the map.
You really need to read up on iterators in the STL, yu're not going to
get very far without them.
john
Hi,
I tried the iterators. Here is the next phase of my problem.
Assume I get references inside map<stirng, unsigned>. Now, I need to
store this references inside a set, that is set<reference_t ype>.
If reference_type is map<...>::itera tor then the problem is that
elements of reference_type cannot be stored in a set as they need to be
comparable with "<".
So, the full problem is that I need to store references to a map<...in
a set<...>.
Thanks a lot,
Ray
Rares Vernica wrote:
John Harrison wrote:
>Rares Vernica wrote:
>>Hi,
How can I save a reference inside a container?
For example I have: map<string, unsignedX;
I would like to be able to save a reference to a position inside X.
For a vector, the reference would be the index inside the vector. For map the reference would be the key (in this case a string). The problem is that I don't want to store the string as it might be too long. I would like to have a smaller size reference, like an unsigned or a pointer.
Thanks, Ray
Use an iterator, that's what they're for.
typedef map<string, unsignedsu_map;
su_map X; X["abc"] = 1; X["def"] = 2; X["ghj"] = 3; X["wer"] = 4;
su_map::iterat or i = X.find("def");
i is now a 'reference' to the position of ("def", 2) inside the map.
You really need to read up on iterators in the STL, yu're not going to get very far without them.
john
Hi,
I tried the iterators. Here is the next phase of my problem.
Assume I get references inside map<stirng, unsigned>. Now, I need to
store this references inside a set, that is set<reference_t ype>.
If reference_type is map<...>::itera tor then the problem is that
elements of reference_type cannot be stored in a set as they need to be
comparable with "<".
So, the full problem is that I need to store references to a map<...in
a set<...>.
Thanks a lot,
Ray
When you need a set or map, but the elements of the set or map doesn't
have a predefined operator< (or the predefined one isn't what you want)
all you have to do is define your own.
It looks complicated but really is quite simple once you know the form.
Here's an example, you can look up the details in a book on the STL.
#include <map>
#include <set>
#include <string>
#include <functional>
using namespace std;
typedef map<string, unsignedsu_map;
typedef su_map::iterato r su_map_iter;
struct su_map_iter_les s_then : public binary_function <su_map_iter,
su_map_iter, bool>
{
bool operator()(su_m ap_iter x, su_map_iter y) const
{
return x->first < y->first;
}
};
int main()
{
su_map m;
m["abc"] = 1;
m["def"] = 2;
set<su_map_iter , su_map_iter_les s_thens;
s.insert(m.find ("abc"));
s.insert(m.find ("def"));
}
The class su_map_iter_les s_then is what defines 'less than' for the set
s in the function main. It's an example of what's called a function
object or functor.
john This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
by: kaede |
last post by:
Hi all,
Consider the following code fragment:
// some data structure
class Data { ... }
// Container for the data structure
Class Container
{
|
by: Jason Heyes |
last post by:
To my understanding, std::vector does not use reference counting to avoid
the overhead of copying and initialisation. Where can I get a reference
counted implementation of std::vector? Thanks.
|
by: Steve Jorgensen |
last post by:
I just came up with a really tidy little solution to the VB/VBA circular
reference issue. It only works with Access 2000 or newer, but that's about
the only down-side.
The issue...
You need an object model that includes a container object, and the object in
the container need to interact with the container itself. The problem is
that, to access the container, each item needs a reference to the container,
and that constitutes a...
|
by: Mortos |
last post by:
I need some quick advice.
I just need to reference a containing class from the nested class. I'm
familiar with Java but C# is proving tricky.
public BigClass {
public int ID_BigClass = -99;
public MiniClass{
public void MiniFunc(){
|
by: Adam |
last post by:
We have a web site that uses .vb for the web pages and .cs for a class
module. We are getting the error in .NET 2.0 and VS 2005 beta 2. It does
work with .NET 1.1.
When trying to access a page that needs the class module I get an error on
web site:
Object reference not set to an instance of an object
Here is where the error is:
| |
by: toton |
last post by:
Hi,
I have a little design related problem, and finding a good way to
resolve it.
To state the problem, I have points from writing of several documents.
Each document represents a Session class , and a SessionManager holds a
deque of Session.
Session holds deque of Page for that document. Page in turn holds
vector of Char in that page.
However Char do not hold the Point associated with that Char. Instead
it holds a pair of iterator for...
|
by: John Henry |
last post by:
Hi list,
Just to make sure I understand this.
Since there is no "pointer" type in Python, I like to know how I do
that.
For instance, if I do:
...some_huge_list is a huge list...
|
by: Astley Le Jasper |
last post by:
Sorry for the numpty question ...
How do you find the reference name of an object?
So if i have this
bob = modulename.objectname()
how do i find that the name is 'bob'
|
by: AK |
last post by:
Hello,
I need to do the following with an xml document which has a list of
assets:
1. Hash the assets
2. Hash the element describing the assets
3. Create a digital signature (using X.509 certificate) over the
hashes from step 1 and 2
Most of the examples I've been looking at are doing a digital
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look !
Part I. Meaning of...
|
by: Hystou |
last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it.
First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
| |
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth.
The Art of Business Website Design
Your website is...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own....
Now, this would greatly impact the work of software developers. The idea...
|
by: conductexam |
last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one.
At the time of converting from word file to html my equations which are in the word document file was convert into image.
Globals.ThisAddIn.Application.ActiveDocument.Select();...
|
by: TSSRALBI |
last post by:
Hello
I'm a network technician in training and I need your help.
I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs.
The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols.
I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
|
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
| |
by: bsmnconsultancy |
last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...
| |