Attachment 367 Details for Bug 231 – Three functions for 2D index arithmetic.

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Three functions for 2D index arithmetic.

IndexArithmetics.h (text/plain), 1.67 KB, created by Hauke Heibel on 2013-07-03 09:13:33 UTC

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Creator: Hauke Heibel

Created: 2013-07-03 09:13:33 UTC

Size: 1.67 KB

patch

obsolete

>#pragma once
>
>/**
> * \brief Increments a 2D index such that it points to the next element.
> * \param index The current index into a matrix/array. It will be modified by the function.
> * \param extents The size of the matrix/array. Required for switching between rows.
> **/
>void increment(Eigen::Vector2i& index, const Eigen::Vector2i& extents)
>{
>  ++index.x();
>  if (index.x() >= extents.x())
>  {
>    index.x() = 0;
>    ++index.y();
>  }
>}
>
>/**
> * \brief Decrements a 2D index such that it points to the previous element.
> * \param index The current index into a matrix/array. It will be modified by the function.
> * \param extents The size of the matrix/array. Required for switching between rows.
> **/
>void decrement(Eigen::Vector2i& index, const Eigen::Vector2i& extents)
>{
>  --index.x();
>  if (index.x() < 0)
>  {
>    index.x() = extents.x()-1;
>    --index.y();
>  }
>}
>
>/**
> * \brief Advances (forward and backward) a 2D index.
> * \param index The current index into a matrix/array. It will be modified by the function.
> * \param extents The size of the matrix/array. Required for switching between rows.
> **/
>template <typename difference_type>
>void advance(difference_type offset, Eigen::Vector2i& index, const Eigen::Vector2i& extents)
>{
>  index.x() += offset;
>
>  // This code has been evaluated for performance on MSVC 2012; switching temporarily to float
>  // is faster than using pure integer arithmetic with modulo/remainder operations and also
>  // faster than using std::div.
>  difference_type delta = static_cast<difference_type>(std::floor(index.x() / static_cast<float>(extents.x())));
>  index.x() -= delta*extents.x();
>  index.y() += delta;
>}

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