Equality Comparisons (== and !=)

Equality is tested for by applying operator == () the to successive element's from each tuple in turn, the operation terminates [1] as soon as two elements are unequal.

• The order of testing is from item 0 (tuple.at< 0 >()) to item tuple.size() - 1.

  ntuple< int, int, int > a( 1, 2, 3 ), b( 2, 0, 0 ), c( a );
  
  CHECK( a != b );
  CHECK( a == c );
  
  std::cout << std::boolalpha << a << " (op) " << b << '\n';
  std::cout << "== " << (a == b) << '\n';
  std::cout << "!= " << (a != b) << std::endl;
  

Test Result: gcc34 Passed, msvc80 Passed, msvc71 Passed

Output

(1,2,3) (op) (2,0,0)
== false
!= true

• The operators will work on different types of tuple.

  • Both tuples must be the same length, left.size() == right.size().
  • Each element must be testable (with operator == ()) with the corresponding element of the other tuple.

  ntuple< int, int, int > a( 1, 2, 3 );
  ntuple< int, short, double > b( 2, 0, 0 ), c( 1, 2, 3 );
  
  CHECK( a != b );
  CHECK( a == c );
  
  std::cout << std::boolalpha << std::showpoint << a << " (op) " << b << '\n';
  std::cout << "== " << (a == b) << '\n';
  std::cout << "!= " << (a != b) << std::endl;
  

Test Result: gcc34 Passed, msvc80 Passed, msvc71 Passed

Output

(1,2,3) (op) (2,0,0.000000)
== false
!= true

• The operation will not compile if both tuples are different lengths (.size()).

  ntuple< int, int, int > a( 1, 2, 3 );
  ntuple< int, int > b( 2, 0 );
  
  assert( a != b );
  

Test Result: gcc34 Passed, msvc80 Passed, msvc71 Passed

Warning

../ntuple-compare.hpp:122:
: 'bool imp::ntuple_s::equal_cons_helper(const imp::ntuple_s::cons<LH,imp::ntuple_s::null_type> &,const imp::ntuple_s::cons<RH,imp::ntuple_s::null_type> &)' : could not deduce template argument for 'const imp::ntuple_s::cons<Tail,imp::ntuple_s::null_type> &' from 'const imp::ntuple_s::cons<Head,Tail>::remainder_type'
        with
        [
            Head=int,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:133:
see declaration of 'imp::ntuple_s::equal_cons_helper'
../ntuple-compare.hpp:122:
see reference to function template instantiation 'bool imp::ntuple_s::equal_cons_helper<A1,imp::ntuple_s::cons<Head,Tail>,A2,imp::ntuple_s::null_type>(const imp::ntuple_s::cons<Head,imp::ntuple_s::cons<Head,Tail>> &,const imp::ntuple_s::cons<Head,Tail> &)' being compiled
        with
        [
            A1=int,
            Head=int,
            Tail=imp::ntuple_s::null_type,
            A2=int
        ]
../ntuple-compare.hpp:151:
see reference to function template instantiation 'bool imp::ntuple_s::equal_cons_helper<Lv_t,Lr_t,Rv_t,Rr_t>(const imp::ntuple_s::cons<Head,Tail> &,const imp::ntuple_s::cons<Head,imp::ntuple_s::cons<Head,imp::ntuple_s::null_type>> &)' being compiled
        with
        [
            Head=int,
            Tail=imp::ntuple_s::cons<int,imp::ntuple_s::cons<int,imp::ntuple_s::null_type>>
        ]
../ntuple-compare.hpp:163:
see reference to function template instantiation 'imp::meta::enable_t_<__formal,Type>::type imp::ntuple_s::operator ==<L,R>(const L &,const R &)' being compiled
        with
        [
            __formal=true,
            Type=bool,
            L=imp::ntuple_s::ntuple<int,int,int>,
            R=imp::ntuple_s::ntuple<int,int>
        ]
./gensrc/more-compare-id-eq-diff-lengths.cpp:26:
see reference to function template instantiation 'imp::meta::enable_t_<__formal,Type>::type imp::ntuple_s::operator !=<imp::ntuple_s::ntuple<A0,A1,A2>,imp::ntuple_s::ntuple<A0,A1>>(const L &,const R &)' being compiled
        with
        [
            __formal=true,
            Type=bool,
            A0=int,
            A1=int,
            A2=int,
            L=imp::ntuple_s::ntuple<int,int,int>,
            R=imp::ntuple_s::ntuple<int,int>
        ]
../ntuple-compare.hpp:122:
: 'bool imp::ntuple_s::equal_cons_helper(const imp::ntuple_s::cons<LH,LT> &,const imp::ntuple_s::cons<RH,RT> &)' : could not deduce template argument for 'const imp::ntuple_s::cons<T3,T4> &' from 'const imp::ntuple_s::cons<Head,Tail>::remainder_type'
        with
        [
            Head=int,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:117:
see declaration of 'imp::ntuple_s::equal_cons_helper'

• The operation will not compile if any two elements can't be tested with operator == ().

  #include <cassert>
  #include "imp/ntuple.hpp"
  using namespace imp;
  
  struct Empty {};
  
  int main()
  {
    ntuple< int, Empty > a( 1, Empty() ), b( 1, Empty() );
  
    assert( a == b );
  }
  

Test Result: gcc34 Passed, msvc80 Passed, msvc71 Passed

Warning

../ntuple-compare.hpp:135:
: Failed to specialize function template 'meta::enable<imp::meta::bool_and<imp::ntuple_s::is_ntuple<L>,imp::ntuple_s::is_ntuple<R>>,bool>::type imp::ntuple_s::operator ==(const L &,const R &)'
        With the following template arguments:
        'imp::ntuple_s::cons<Head,Tail>::first_type'
        with
        [
            Head=Empty,
            Tail=imp::ntuple_s::null_type
        ]
        'imp::ntuple_s::cons<Head,Tail>::first_type'
        with
        [
            Head=Empty,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:122:
see reference to function template instantiation 'bool imp::ntuple_s::equal_cons_helper<A1,A1>(const imp::ntuple_s::cons<Head,Tail> &,const imp::ntuple_s::cons<Head,Tail> &)' being compiled
        with
        [
            A1=Empty,
            Head=Empty,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:151:
see reference to function template instantiation 'bool imp::ntuple_s::equal_cons_helper<Lv_t,Lr_t,Rv_t,Rr_t>(const imp::ntuple_s::cons<Head,Tail> &,const imp::ntuple_s::cons<Head,Tail> &)' being compiled
        with
        [
            Head=int,
            Tail=imp::ntuple_s::cons<Empty,imp::ntuple_s::null_type>
        ]
./gensrc/more-compare-id-no-eq.cpp:11:
see reference to function template instantiation 'imp::meta::enable_t_<__formal,Type>::type imp::ntuple_s::operator ==<imp::ntuple_s::ntuple<A0,A1>,imp::ntuple_s::ntuple<A0,A1>>(const L &,const R &)' being compiled
        with
        [
            __formal=true,
            Type=bool,
            A0=int,
            A1=Empty,
            L=imp::ntuple_s::ntuple<int,Empty>,
            R=imp::ntuple_s::ntuple<int,Empty>
        ]
../ntuple-compare.hpp:135:
: binary '==' : 'const imp::ntuple_s::cons<Head,Tail>::first_type' does not define this operator or a conversion to a type acceptable to the predefined operator
        with
        [
            Head=Empty,
            Tail=imp::ntuple_s::null_type
        ]

Ordering Comparisons (<, <<=, > and >=)

Orderd comarison of ntuple<>'s are done with an element wise (from 0 to tuple.size() - 1) application of operator's == and <.

• Elements are tested with == until a pair returns false then < is applied

• The other 3 operators (<=, > and >=) are synthesized from the results of the < operation:

  l <= r	! ( r < l )
  l > r	( r < l )
  l >= r	! ( l < r )

ntuple< int, int, int > a( 3, 2, 1 ), b( 3, 2, 0 );

CHECK( a > b && a >= b && b < a && b <= a );
CHECK( !(a < b) && !(a <= b) && !(b > a) && !(b >= a) );

std::cout << std::boolalpha << a << " op " << b;
std::cout
  << "\n<  " << ( a < b )
  << "\n<= " << ( a <= b )
  << "\n>  " << ( a > b )
  << "\n>= " << ( a >= b )
  << std::endl
;

Test Result: gcc34 Passed, msvc80 Passed, msvc71 Passed

Output

(3,2,1) op (3,2,0)
<  false
<= false
>  true
>= true

• ntuple<>'s of different lengths (tuple.size()) can't be compared.

ntuple< int, int > a( 1, 2 );
ntuple< int, int, int > b( 1, 2, 3 );

CHECK( a < b );

Test Result: gcc34 Passed, msvc80 Passed, msvc71 Passed

Warning

../ntuple-compare.hpp:22:
: 'bool imp::ntuple_s::less_cons_helper(const imp::ntuple_s::cons<LH,imp::ntuple_s::null_type> &,const imp::ntuple_s::cons<RH,imp::ntuple_s::null_type> &)' : could not deduce template argument for 'const imp::ntuple_s::cons<Head,imp::ntuple_s::null_type> &' from 'const imp::ntuple_s::cons<Head,Tail>::remainder_type'
        with
        [
            Head=int,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:51:
see declaration of 'imp::ntuple_s::less_cons_helper'
../ntuple-compare.hpp:22:
see reference to function template instantiation 'bool imp::ntuple_s::less_cons_helper<A1,imp::ntuple_s::null_type,A0,imp::ntuple_s::cons<Head,Tail>>(const imp::ntuple_s::cons<Head,Tail> &,const imp::ntuple_s::cons<Head,imp::ntuple_s::cons<Head,Tail>> &)' being compiled
        with
        [
            A1=int,
            A0=int,
            Head=int,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:68:
see reference to function template instantiation 'bool imp::ntuple_s::less_cons_helper<Lv_t,Lr_t,Rv_t,Rr_t>(const imp::ntuple_s::cons<Head,Tail> &,const imp::ntuple_s::cons<Head,imp::ntuple_s::cons<Head,Tail>> &)' being compiled
        with
        [
            Head=int,
            Tail=imp::ntuple_s::cons<int,imp::ntuple_s::null_type>
        ]
./gensrc/more-compare-id-cmp-diff.cpp:26:
see reference to function template instantiation 'imp::meta::enable_t_<__formal,Type>::type imp::ntuple_s::operator <<imp::ntuple_s::ntuple<A0,A1>,imp::ntuple_s::ntuple<A0,A1,A2>>(const L &,const R &)' being compiled
        with
        [
            __formal=true,
            Type=bool,
            A0=int,
            A1=int,
            A2=int,
            L=imp::ntuple_s::ntuple<int,int>,
            R=imp::ntuple_s::ntuple<int,int,int>
        ]
../ntuple-compare.hpp:22:
: 'bool imp::ntuple_s::less_cons_helper(const imp::ntuple_s::cons<LH,LT> &,const imp::ntuple_s::cons<RH,RT> &)' : could not deduce template argument for 'const imp::ntuple_s::cons<Head,Tail> &' from 'const imp::ntuple_s::cons<Head,Tail>::remainder_type'
        with
        [
            Head=int,
            Tail=imp::ntuple_s::null_type
        ]
../ntuple-compare.hpp:18:
see declaration of 'imp::ntuple_s::less_cons_helper'

---

[1]	This "Short circuiting" is provided by the inbuilt operator &&.