/**************************************************************************\MODULE: pairSUMMARY:Macros are defined providing template-like classes for pairs.The macro NTL_pair_decl(S,T,pair_S_T) declares a class pair_S_T whoseimplementation can be instatntiated with NTL_pair_impl(S,T,pair_S_T).  It ispresumed that the underlying types have a default constructor, a copyconstructor, and assignment operator, and a destructor (this isnormally the case for most types).If S and T support I/O operator << and >>, then pair_S_T can be madeto support these operators as well using NTL_pair_io_decl(S,T,pair_S_T) andNTL_pair_io_impl(S,T,pair_S_T).The same goes for the equaltity operators == and != usingNTL_pair_eq_decl(S,T,pair_S_T) and NTL_pair_eq_impl(S,T,pair_S,T).The decalaration    pair_S_T p;creates a pair object using the default constructors for S and T.  Themember p.a is the first component (of type S) and the member p.b isthe second component (of type T).\**************************************************************************/#include <NTL/tools.h>class pair_S_T {  public:     S a;     T b;       pair_S_T();    // default constructor...invokes default constructors for S and T   pair_S_T(const pair_S_T& x); // copy   pair_S_T& operator=(const pair_S_T& x); // assignment   pair_S_T(const S& x, const T& y);  // initialize with (x, y)   ~pair_S_T();    // destructor...invokes destructors for S and T};    pair_S_T cons(const S& x, const T& y); // returns pair_S_T(x, y)/**************************************************************************\                             Input/OutputThe I/O operators can be declared with NTL_pair_io_decl(S,T,pair_S_T), andimplemented using NTL_pair_io_impl(S,T,pair_S_T).  Elements are read and written using the underlying I/O operators << and >> for S and T.The I/O format for a pair_a_b is   [a b]\**************************************************************************/istream& operator>>(istream&, pair_S_T&);  ostream& operator<<(ostream&, const pair_S_T&);  /**************************************************************************\                              Equality TestingThe equality testing operators == and != can be declared withNTL_pair_eq_decl(S,T,pair_S_T) and implemented with NTL_pair_eq_impl(S,T,pair_S,T).  The tests are performed using the underlying operator == for S and T.\**************************************************************************/long operator==(const pair_S_T& x, const pair_S_T& y);long operator!=(const pair_S_T& x, const pair_S_T& y);