map template class

[nickyeng]

Hi,

i want to take a look at STL Associative Container, map.

but i can't find in google. Maybe i use the term to search.

stop by here, and ask for help.

actually, i have to create associative array template class similiary to map<string, int> container.

That's why i wanna take a look at the map template class code.

can anyone show me?

thanks in advance.
Nicky Eng.

[horace1]

have a look at
http://pages.cpsc.ucalgary.ca/~kremer/STL/1024x768/index.html
http://www.josuttis.com/libbook/idx.html

[nickyeng]

thanks for the links.

but i still can't find out how to create template class like map container, something like this template<class Key, class T> without using any STL facilities.

[horace1]

thanks for the links.

but i still can't find out how to create template class like map container, something like this template<class Key, class T> without using any STL facilities.

for an example have a look at the CMapEx class
http://www.codeproject.com/cpp/extcol.asp

[nickyeng]

i want something like this:

template<class K, class T>
    class AssocArray {
    public:
        explicit inline AssocArray(int = 1);    // constructor
        inline T& operator[] (const K& k);    // access element with key k
 
      private:
        int capacity;
        K* k;
        T* t;
        };
         /*** constrcutor ***/
        template<class K, class T>
        inline AssocArray<K, T>::AssocArray(int s) {
        if(s <= 0) {
            s = 1;
        }
        capacity = s;
        k = new K[s];
        // initialize variable t here, but i'm not sure how to initialise it.
    }
 
        template<class K, class T>
    inline AssocArray<T>::operator[] (const AssocArray<K>& k) {
        // do something here..
    }
 

and the in the ccp file, i test the array, buy using this:

AssocArray<string, int> arr;
string str;
int i;
 
arr[str] = i;
// of course must use other operators here, 
//i just showing example and hope you guys understand what im trying to ask.
 

I CAN'T use any STL facilities in template class.
By the way, could anyone give example of code of what should i code in the comment part above, esp operator[] function.

thanks in advance.
Nicky Eng.

[horace1]

i want something like this:
I CAN'T use any STL facilities in template class.
By the way, could anyone give example of code of what should i code in the comment part above, esp operator[] function.

thanks in advance.
Nicky Eng.

have a look at
http://www.thescripts.com/forum/thread580637.html

[horace1]

are you looking for something like this?

template<class K, class T>
    class AssocArray {
    public:
        explicit inline AssocArray(int = 1);    // constructor
        inline T& operator[] (const K& k);    // access element with key k
        inline int size() { return asize;}
      private:
        int capacity;
        int asize;
        K* k;
        T* t;
        };
         /*** constrcutor ***/
        template<class K, class T>
        inline AssocArray<K, T>::AssocArray(int s) {
        if(s <= 0) {
            s = 1;
        }
        capacity = s;
        k = new K[s];
        t = new T[s];
        asize=0;
    }
 
   template<class K, class T>
    inline T& AssocArray<K, T>::operator[] (const K& k1) {
           // look for existing key - if found return reference to  it
           for(int i=0; i<asize;i++)
              if(k[i]==k1) return t[i];
           // add new key, return reference to it
           k[asize]=k1;
           return t[asize++];
    }
 

if you try

    AssocArray<string, int> arr(10);
    arr["one"]=1;
    arr["two"]=2;
    arr["three"]=3;
    cout << arr["one"] << endl;
    cout << arr["two"] << endl;
    cout << arr["three"] << endl;
    arr["two"]=20;
    arr["three"]=300;
    cout << arr["one"] << endl;
    cout << arr["two"] << endl;
    cout << arr["three"] << endl;
 

it gives
1
2
3
1
20
300

[nickyeng]

thanks horace1.

you helped me alot.

i will come back when i have questions.

thanks again.
:D

from
Nicky Eng.

[nickyeng]

hi ,

i had my template class created, and compiled well at the first place.

after i change some code, and then i regreted and change back to what it used to be.

and it give me this error:

assocarray.h:54: internal compiler error: Segmentation fault
Please submit a full bug report, 
with preprocessed source if appropriate
See <URL:http://gcc.gnu.org/bugs.html> for instructions
 

here is the code:

#ifndef _ASSOCARRAY_H_
#define _ASSOCARRAY_H_
 
namespace Array {
 
    template<class K, class T>
    class AssocArray {
    public:
        explicit inline AssocArray(int = 1);    // constructor
        inline T& operator[] (K& k);    // access element with key k
        inline bool find (K& k);
        inline int size() { return asize;}
    private:
        int capacity;
        int asize;
        K* k;
        T* t;
    };
 
 
    /*** constrcutor ***/
    template<class K, class T>
        inline AssocArray<K, T>::AssocArray(int s) {
            if(s <= 0) {
                s = 1;
            }
            capacity = s;
            k = new K[s];
            t = new T[s];
            asize=0;
        }
 
    template<class K, class T>
        inline T& AssocArray<K, T>::operator[] (K& k1) {
            // look for existing key - if found return reference to  it
            for(int i=0; i<asize;i++)
                if(k[i]==k1) return t[i];
            // add new key, return reference to it
                k[asize]=k1;
                return t[asize++];
    }
 
    template<class K, class T>
    inline bool AssocArray<K, T>::find (K& k1) {
        // look for existing key - if found return reference to  it
        for(int i=0; i<asize;i++) {
            if(k[i]==k1) {
                return true;
            }
        }
 
        return false;
    }
 
}
#endif
 

any ideas?

[horace1]

looks fines - I ran the following thru two gcc compilers without problems - the only change to your code is to make the parameter of operator[] a const so you can have expressions such as arr["one"]

#include <iostream>
#include <string>
using namespace std;
 
#ifndef _ASSOCARRAY_H_
#define _ASSOCARRAY_H_
 
namespace Array {
 
    template<class K, class T>
    class AssocArray {
    public:
        explicit inline AssocArray(int = 1);    // constructor
          // ** added const
        inline T& operator[] (const K& k);    // access element with key k
        inline bool find (K& k);
        inline int size() { return asize;}
    private:
        int capacity;
        int asize;
        K* k;
        T* t;
    };
 
 
    /*** constrcutor ***/
    template<class K, class T>
        inline AssocArray<K, T>::AssocArray(int s) {
            if(s <= 0) {
                s = 1;
            }
            capacity = s;
            k = new K[s];
            t = new T[s];
            asize=0;
        }
 
    template<class K, class T>
        inline T& AssocArray<K, T>::operator[] (const K& k1) {  // ** added const
            // look for existing key - if found return reference to  it
            for(int i=0; i<asize;i++)
                if(k[i]==k1) return t[i];
            // add new key, return reference to it
                k[asize]=k1;
                return t[asize++];
    }
 
    template<class K, class T>
    inline bool AssocArray<K, T>::find (K& k1) {
        // look for existing key - if found return reference to  it
        for(int i=0; i<asize;i++) {
            if(k[i]==k1) {
                return true;
            }
        }
 
        return false;
    }
 
}
 
#endif
 
using namespace Array;
 
int main()
{
    AssocArray<string, int> arr(10);
    arr["one"]=1;
    arr["two"]=2;
    arr["three"]=3;
    cout << arr["one"] << endl;
    cout << arr["two"] << endl;
    cout << arr["three"] << endl;
    arr["two"]=20;
    arr["three"]=300;
    cout << arr["one"] << endl;
    cout << arr["two"] << endl;
    cout << arr["three"] << endl;
    cin.get();
}
 

[nickyeng]

thanks again.

i think it compiled okay. i mean preivous code.
What i have to do is ignore the "internal compiler error" issues.

i still can run my testfile.cpp.

thanks.
from
Nicky Eng

[nickyeng]

dear Horace1,

i noticed that it only can have 10 element.

what if i declare this:

AssocArray<string, int> a;
 

i want when it reach the limit of capacity, it will double its allocated size each time run out of space. done in template class.

here is my code and it runs okay with declaration above i made.

#ifndef _ASSOCARRAY_H_
#define _ASSOCARRAY_H_
#include <string>
 
namespace Array {
    using std::string;
 
    template<class K, class T>
    class AssocArray {
    public:
        explicit inline AssocArray(int = 1);  
        inline T& operator[] (K& k);    // non const
        inline const T& operator[] (K& k) const;    // const ref
        inline int size() { return asize;}
    private:
        int capacity;
        int asize;
        K* k;
        T* t;
        inline void resize(int);
    };
 
    class BadSubscript {
    public:
        BadSubscript(const std::string& err) : msg(err){}
        const std::string& Message() const { return msg; }
 
    private:
            const std::string msg;
    };
 
    /*** constrcutor ***/
    template<class K, class T>
    inline AssocArray<K, T>::AssocArray(int s) {
        if(s <= 0) {
            s = 1;
        }
        capacity = s;
        k = new K[s];
        t = new T[s];
        asize=0;
    }
 
    template<class K, class T>
    inline T& AssocArray<K, T>::operator[] (K& k1) {
 
        if (asize >= capacity ) {
            if (asize <= capacity*2 ) {
                resize(capacity * 2);
            } else {
                resize(asize + 1);
            }
        }
            k[asize] = k1;
            return t[asize++];
    }
 
    template<class K, class T>
    inline const T& AssocArray<K, T>::operator[] (K& k1) const{
        // look for existing key - if found return reference to  it
        for(int i=0; i<asize;i++) {
            if(k[i]==k1) {
                return t[i];
            }
        }
        throw BadSubscript("The word is not found! ");
    }
 
    template<class K, class T>
    inline void AssocArray<K, T>::resize(int s) {
        if (s > capacity) {
            K* k1 = new K[s];
            T* t1 = new T[s];
 
            for(int i= 0; i < asize; i++) {
                k1[i] = k[i];
                t1[i] = t[i];
            }
            delete[] k;
            delete[] t;
 
            k = k1;
            t = t1;
        }
        capacity = s;
    }
}
#endif
 

specially thanks to horace1.
thanks alot.