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generate(3C++)			       -			generate(3C++)

Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.

NAME
       generate, generate_n

	-  Initialize  a  container  with values produced by a value-generator
       class.

SYNOPSIS
#include <algorithm>

template <;class ForwardIterator, class Generator>
 void generate(ForwardIterator first, ForwardIterator last,
	       Generator gen);

template <;class OutputIterator, class Size, class Generator>
 void generate_n(OutputIterator first, Size n, Generator gen);

DESCRIPTION
       A value-generator function returns a value each time it is invoked. The
       algorithms  generate  and  generate_n  initialize  (or  reinitialize) a
       sequence by assigning the return value of the generator function gen to
       all  the elements designated by iterators in the range [first, last) or
       [first, first + n). The function gen takes no arguments. (gen can be  a
       function	 or  a	class  with an operator () defined that takes no argu‐
       ments.)

       generate_n assumes that there are at least n elements following	first,
       unless first is an insert iterator.

COMPLEXITY
       The generate and generate_n algorithms invoke gen and assign its return
       value exactly last - first (or n) times.

EXAMPLE
//
// generate.cpp
//
 #include <algorithm>
 #include <vector>
 #include <iostream>
using namespace std;

 // Value generator simply doubles the current value
 // and returns it
template <;class T>
class generate_val
 {
  private:
     T val_;
  public:
     generate_val(const T& val) : val_(val) {}
     T& operator()() { val_ += val_; return val_; }
 };

int main()
 {
  int d1[4] = {1,2,3,4};
  generate_val<int> gen(1);

   // Set up two vectors
  vector<int> v1(d1,d1 + 4), v2(d1,d1 + 4);
   // Set up one empty vector
  vector<int> v3;

   // Generate values for all of v1
   generate(v1.begin(),v1.end(),gen);

   // Generate values for first 3 of v2
   generate_n(v2.begin(),3,gen);

   // Use insert iterator to generate 5 values for v3
   generate_n(back_inserter(v3),5,gen);

   // Copy all three to cout
  ostream_iterator<int,char> out(cout," ");
  copy(v1.begin(),v1.end(),out);
  cout << endl;
  copy(v2.begin(),v2.end(),out);
  cout << endl;
  copy(v3.begin(),v3.end(),out);
  cout << endl;

   // Generate 3 values for cout
   generate_n(ostream_iterator<int>(cout," "),3,gen);
  cout << endl;

  return 0;
 }

Program Output

2 4 8 16
2 4 8 4
2 4 8 16 32
2 4 8

WARNINGS
       If your compiler does not support default template parameters, then you
       always  need  to	 supply the Allocator template argument. For instance,
       you have to write:

       vector<int, allocator<int> >

       instead of:

       vector<int>

       If your compiler does not support namespaces, then you do not need  the
       using declaration for std.

SEE ALSO
       Function_Objects

Rogue Wave Software		  02 Apr 1998			generate(3C++)
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