Index.h

Classes

Index -- Interconvert between 0 and 1 based relative indexing. (full description)

class Index

Interface

Public Members

Index(Int zeroRelValue=0) : local_value_p(zeroRelValue)

Index(uInt zeroRelValue) : local_value_p(zeroRelValue)

Index(const Index &other) : local_value_p(other.local_value_p)

Index &operator=(const Index &other)

~Index()

Int operator()() const

Int zeroRelativeValue() const

Int oneRelativeValue() const

static void convertVector(Vector<Int> &out, const Vector<Index> &in, Bool outValuesAreLocal=True)

static void convertVector(Vector<Index> &out, const Vector<Int> &in, Bool inValuesAreLocal=True)

static void convertIPosition(IPosition &out, const Vector<Index> &in, Bool outValuesAreLocal=True)

static void convertIPosition(Vector<Index> &out, const IPosition &in, Bool inValuesAreLocal=True)

Description

Review Status

Reviewed By:

David Barnes

Date Reviewed:

1998/12/01

Programs:

Tests:

tIndex

Synopsis

This class is used to help reduce the chance of error when dealing with index values which are generated where indexing is 1-based (Glish), and used where indexing is 0-based (C++). Typical examples of such indices include:

The position of a pixel in an image or an array (use Vector<Index>).
The row number of a table (use an Index scalar).

In general, consistent use of Index for all such locations should greatly reduce the likelihood of off by one errors. The Index will generally appear as the argument to a member function which is available to the Glish user through the Tasking system, however it is not coupled to the Tasking system in any way.

Of course you should only use Index for 0 or 1 relative locations. Actual "counts" should remain integers.

Example

Suppose we want to work on a Table row which is specified by a user:

    void SomeClass::someFunc(Table &table, Index row)
    {
        ScalarColumn<Float> col(table, "col");
        Float x = col(row()); // Index::operator() returns 0-relative value
    }

Suppose we wanted to perform some operation on a subsection of an image defined by a blc and trc which is to be specified by the user. We should code the function as follows:

       void SomeClass::someFunc(ImageInterface<Float> &inout,
                                const Vector<Index> &blc,
                                const Vector<Index> &trc)
    {
       // Turn blc,trc into IPositions
       IPosition iblc, itrc;
       Index::convertIPosition(iblc, blc);
       Index::convertIPosition(itrc, trc);
       ... perform computation ...
    }

Motivation

Encapsulate the indexing difference between Glish (1-based) and C++ (0-based).

To Do

Nothing known.

Member Description

Index(Int zeroRelValue=0) : local_value_p(zeroRelValue)
Index(uInt zeroRelValue) : local_value_p(zeroRelValue)

Construct an index from a zero-relative value. The default is zero, i.e. the first position of the container.

Index(const Index &other) : local_value_p(other.local_value_p)
Index &operator=(const Index &other)

Make a copy of other.

~Index()

Int operator()() const
Int zeroRelativeValue() const

Return the local, i.e. zero-relative, value.

Int oneRelativeValue() const

Return the canonical value, i.e. zeroRelativeValue()+1.

static void convertVector(Vector<Int> &out, const Vector<Index> &in, Bool outValuesAreLocal=True)
static void convertVector(Vector<Index> &out, const Vector<Int> &in, Bool inValuesAreLocal=True)
static void convertIPosition(IPosition &out, const Vector<Index> &in, Bool outValuesAreLocal=True)
static void convertIPosition(Vector<Index> &out, const IPosition &in, Bool inValuesAreLocal=True)

Interconvert between Vector<Index> and IPosition as well as Vector<Index> and Vector<Int>. If necessary, the output values are resized. The default is that the IPosition/Vector<Int> values are in local (0-relative) format, however this may be changed. Generally this default will only be changed by the Tasking system itself.