Standard C++ LibraryCopyright 1996, 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 arguments.)

  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.h>

   // 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;
   }

  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
  need to always supply the Allocator template argument.  For instance,
  you'll have to write:

  vector<int, allocator<int> >

  instead of :

  vector<int>

SEE ALSO

  function objects

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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