Algorithm Interfaces
Some algorithms require more powerful iterators than others. For example, sort() only works with random access iterators. Because a vector has random access iterators, the following example compiles and works correctly.
Example <ospace/osstd/examples/alg4.cpp>
#include <iostream>
#include <algorithm>
#include <vector>

void
main()
  {
  vector< int > years;
  years.push_back( 1962 );
  years.push_back( 1992 );
  years.push_back( 2001 );
  years.push_back( 1999 );

  sort( years.begin(), years.end() );

  vector< int >::iterator i;
  for ( i = years.begin(); i != years.end(); ++i )
    cout << *i << "\n";
  }

1962
1992
1999
2001

If sort() is used with a less powerful iterator, either a compiler error or a linker error occurs. The following example results in a compiler error, because sort() is attempted on a list that provides only bidirectional iterators.

Example <ospace/osstd/examples/alg5.cpp>
#include <iostream>
#include <algorithm>
#include <list>

// NOTE: This example is NOT supposed to compile.

void
main()
  {
  list< int > years;
  years.push_back( 1962 );
  years.push_back( 1992 );
  years.push_back( 2001 );
  years.push_back( 1999 );

  sort( years.begin(), years.end() ); // Causes linker error.

  list< int >::iterator i;
  for ( i = years.begin(); i != years.end(); ++i )
    cout << *i << "\n";
  }

Many STL algorithms require a predicate, function, or function object as a parameter. For example, the for_each() algorithm applies a supplied function to every item in a sequence. Similarly, the count_if() algorithm counts all the elements in a sequence satisfying a particular predicate. For examples and further information about predicates and function objects, consult the Functions and Function Objects .

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