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generate_n (3)
  • >> generate_n (3) ( Solaris man: Библиотечные вызовы )
  • 
                           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 func-
         tion or a class with an operator () defined  that  takes  no
         arguments.)
    
         generate_n assumes that there are at least n  elements  fol-
         lowing 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  parame-
         ters,  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
    
    
    
    


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