Using Templates in Multi-Dimensional Operator Overloading

Multi- dimensional operator overloading

In the operator overloading chapter, you saw that opDollar, opIndex, and opSlice are for element indexing and slicing. When overloaded for single-dimensional collections, these operators have the following responsibilities:

• opDollar: Returns the number of elements of the collection

• opSlice: Returns an object that represents some or all of the elements of the collection

• opIndex: Provides access to an element

These operator functions have templated versions as well, which have different responsibilities from the non-templated ones above. Note that in multi- dimensional operator overloading opIndex assumes the responsibility of opSlice.

• opDollar template: Returns the length of a specific dimension of the collection. The dimension is determined by the template parameter:

  size_t opDollar(size_t dimension)() const 
  {
      // ...
  }
  

• opSlice template: Returns the range information that specifies the range of elements (e.g., the begin and end values in array[begin..end]). The information can be returned as Tuple!(size_t, size_t) or an equivalent type. The dimension that the range specifies is determined by the template parameter:

  Tuple!(size_t, size_t) opSlice(size_t dimension)(size_t begin,size_t end)
      return tuple(begin, end); 
  }
  

• opIndex template: Returns a range object that represents a part of the collection. The range of elements are determined by the template parameters:

  Range opIndex(A...)(A arguments) {
      // ...
  }
  

opIndexAssign and opIndexOpAssign also have templated versions, which operate on a range of elements of the collection. The user-defined types that define these operators can be used with the multi-dimensional indexing and slicing syntaxes: