Mega Code Archive
Generate_n and int sequence
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/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <list>
#include <algorithm>
using namespace std;
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << ' ';
}
std::cout << std::endl;
}
class IntSequence {
private:
int value;
public:
// constructor
IntSequence (int initialValue)
: value(initialValue) {
}
// ''function call''
int operator() () {
return value++;
}
};
int main()
{
list<int> coll;
IntSequence seq(1); // integral sequence starting with 1
// insert values from 1 to 4
// - pass function object by reference
// so that it will continue with 5
generate_n<back_insert_iterator<list<int> >,
int, IntSequence&>(back_inserter(coll), // start
4, // number of elements
seq); // generates values
PRINT_ELEMENTS(coll);
// insert values from 42 to 45
generate_n (back_inserter(coll), // start
4, // number of elements
IntSequence(42)); // generates values
PRINT_ELEMENTS(coll);
// continue with first sequence
// - pass function object by value
// so that it will continue with 5 again
generate_n (back_inserter(coll), // start
4, // number of elements
seq); // generates values
PRINT_ELEMENTS(coll);
// continue with first sequence again
generate_n (back_inserter(coll), // start
4, // number of elements
seq); // generates values
PRINT_ELEMENTS(coll);
}
1 2 3 4
1 2 3 4 42 43 44 45
1 2 3 4 42 43 44 45 5 6 7 8
1 2 3 4 42 43 44 45 5 6 7 8 5 6 7 8
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