C++ Abstract Datatypes and STL

Contents 1 References 2 vector<> 3 Examples 3.1 List Iteration 3.2 Sorting 3.3 Complex Number 4 Don't Inherit from STL Classes 5 References

References

• C/C++ Reference
• STL Table of Contents
• STL Alphabetical Index
• cplusplus.com Reference - includes strings and streams

vector<>

• The last element in the vector is end()-1
• Iterating beyond end()-1 yields arbitrary results
• Check for membership of n in v: count(v.begin(), v.end(), n) > 0

Examples

List Iteration

#include <iostream>
#include <list>
#include <string>
using namespace std;

class Thing {
public:
    Thing(string text): text(text) {}

protected:
    string text;

    // is declared as friend because it accesses 'text'
    friend ostream& operator <<(ostream& os, const Thing* t); 

};

ostream& operator <<(ostream& os, const Thing* t) {
    return os << t->text << endl;
}

int main(void) {
    list<Thing *> l;
    for(int n = 0; n < 3; n++)
        l.push_back(new Thing("Thingie"));

    for(list<Thing *>::iterator i = l.begin(); i != l.end(); ++i)
        cout << *i;

    return 0;
}

Sorting

bool ordering_relation(Thing *a, Thing *b) {
    return a->value < b->value;
}

vector<Thing> things = new vector<Thing>();

// sort does not maintain order of elements that are equal
sort(things.begin(), things.end(), ordering_relation);

// stable_sort maintains order of equal elements
stable_sort(things.begin(), things.end(), ordering_relation);

Complex Number

#include <complex>
#include <iostream>
using namespace std;

int main(void) {
    complex<float> x(1,2);
    complex<float> y = x / 2.f;
    //y = x / 2.0; error: division with double
    //y = x / 2;   error: division with int
    cout << sin(y) << endl;
    cout << norm(y) << endl;
    return 0;
}

Don't Inherit from STL Classes

It is a common question, "Why shouldn't we inherit a class from STL classes?" The answer to this question is simple—the Big Three rule [CLI95]. In other words, you should have a virtual destructor in a class if you want to make it a base class. However, there isn't any class in STL that defines a virtual destructor. Even if you try to inherit a class from STL class, the compiler doesn't complain about it, although there is a high chance of a resource leak in the program.

--quote from codeguru

Compose instead, e.g. include a list instance in your PrintableList template class:

#include <vector>
#include <iostream>
#include <string>
using namespace std;

template<class T> class PrintableList {
public:
    operator string();
    void operator <<(T stuff) { l.push_back(stuff); }
protected:
    vector<T> l;
};

template<class T> PrintableList<T>::operator string() {

    // vector<T>::iterator i;       // this does not parse, even though it
                                    // makes sense
    typename vector<T>::iterator i; // 'typename' kicks the ass of the parser
                                    // to make it understand that it is a
                                    // type name and not some other arbitrary
                                    // stuff. C++ is kinda stupid that way.
    string s("[");
    for(i = l.begin(); i != l.end()-1; ++i) // here it would make sense to
        s += string(*i) + ", ";             // use the STL algorithm
    return s + string(*i++) + "]";          // 'accumulate'. Unfortunately,
}                                           // it didn't exist in my GNU C++
                                            // library at the time of writing.
int main(void) {
    PrintableList<string> l;
    l << "hewey"; l << "dewey"; l << "luie";
    cout << string(l);
    return 0;
}

References

• http://support.sas.com/documentation/onlinedoc/sasc/doc/cplus/z0274855.htm