floops.hh

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#ifndef INCLUDED_ObjexxFCL_floops_hh
#define INCLUDED_ObjexxFCL_floops_hh


// Fortran Compatible DO Loop Support
//
// Project: Objexx Fortran Compatibility Library (ObjexxFCL)
//
// Version: 3.0.0
//
// Language: C++
//
// Copyright (c) 2000-2009 Objexx Engineering, Inc. All Rights Reserved.
// Use of this source code or any derivative of it is restricted by license.
// Licensing is available from Objexx Engineering, Inc.:  http://objexx.com  Objexx@objexx.com

// Semantics:
//  Fortran:   DO i = b, e, s
//  C++ equiv: for ( std::size_t j = 1, n = floops( i, b, e, s ); j <= n; ++j, i += s )


// C++ Headers
#include <cassert>
#include <cstddef>


namespace ObjexxFCL {


// Fortran DO Loop Control
template< typename I, typename B, typename E, typename S >
inline
std::size_t
floops( I & i, B const & b, E const & e, S const & s ) // DO i = b, e, s
{
  // Initializes the DO variable i and returns the number of iterations count

  // Convert control expressions to type of loop control variable
  I const n1( b );
  I const n2( e );
  I const n3( s );
  I const ZERO( 0 );

  // Initialize loop variable (Fortran does this even if loop never executes)
  i = n1;

  // Get loop count being careful to avoid negative values in case I is an unsigned type
  if ( n1 < n2 ) {
    if ( n3 < ZERO ) {
      return 0;
    } else { // n3 > 0
      assert( n3 > ZERO );
      return ( ( n2 - n1 ) + n3 ) / n3;
    }
  } else if ( n1 > n2 ) {
    if ( n3 > ZERO ) {
      return 0;
    } else { // n3 < 0
      assert( n3 < ZERO );
      return ( ( n1 - n2 ) - n3 ) / -n3;
    }
  } else { // n1 == n2
    // Allow n3 == 0 in this case but Fortran doesn't
    return 1;
  }
}


// Fortran DO Loop Control  with Implicit Step=1
template< typename I, typename B, typename E >
inline
std::size_t
floops( I & i, B const & b, E const & e ) // DO i = b, e
{
  return floops( i, b, e, 1 );
}


} // namespace ObjexxFCL


#endif // INCLUDED_ObjexxFCL_floops_HH