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GrowableArray Class Template Reference

This file defines an array template class that will grow as elements are added to the end of the array. More...

#include <grow_array.h>

List of all members.

Public Methods
	GrowableArray ()
	~GrowableArray ()
	destructor. More...
const size_t	length (void) const
	Length of the data (which is not necessarily the same as the length of the internal array. More...
void	set_to_zero ()
	set array to zero length. More...
T&	operator[] (const size_t i)
	LHS [] operator. More...
T	operator[] (const size_t i) const
	RHS [] operator. More...
const T*	getData () const
	Get a pointer to the internal data array. More...
void	append (T item)
	append an item to the end of the array. More...
void	expand (size_t amount)
	expand. More...
void	remove (void)
	Remove one item from the end of the array. More...
Private Types
enum	bogus { StartArraySize = 128 }
Private Methods
bool	twice ()
	twice. More...
Private Attributes
size_t	num_elem
	number of data elements. More...
size_t	array_size
	Array size (always <= num_elem). More...
T*	pArray

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Detailed Description

template<class T> class GrowableArray

This file defines an array template class that will grow as elements are added to the end of the array.

This is similar to the STL <vector> class.

This array class is designed for dense arrays where the all elements of the array are used.

Usage:

• Elements are added to the end of the array via the append function.

• Elements in the array can be accessed via the [] operator.

• If the elements in the array are dynamicly allocated, the user is responsible for deallocating these elements.

A doubling algorithm is used when the data size is expanded because it minimizes the amount of copying that must be done. The array will quickly grow to a the size needed to accomodate the data set and no more copying will be necessary. For large arrays there is the drawback that more memory may be allocated than is needed, since the amount of memory used grows exponentially.

Author:

Ian Kaplan

Definition at line 69 of file grow_array.h.

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Member Enumeration Documentation

template<class T> enum GrowableArray<T>::bogus [private]

Enumeration values: StartArraySize   Definition at line 71 of file grow_array.h. { StartArraySize = 128 } bogus;

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Constructor & Destructor Documentation

template<class T> GrowableArray<T>::GrowableArray<T> ( ) [inline]

Definition at line 112 of file grow_array.h. { pArray = new T[ StartArraySize ]; num_elem = 0; array_size = StartArraySize; } // GrowableArray constructor

template<class T> GrowableArray<T>::~GrowableArray<T> ( ) [inline]

destructor. Definition at line 120 of file grow_array.h. { if (pArray != NULL) { delete [] pArray; } } // GrowableArray destructor

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Member Function Documentation

template<class T> void GrowableArray<T>::append ( T item ) [inline]

append an item to the end of the array. Definition at line 155 of file grow_array.h. Referenced by packfreq::findLevel(). { if (num_elem == array_size) { bool allocOK = twice(); assert( allocOK ); } pArray[ num_elem ] = item; num_elem++; } // append

template<class T> void GrowableArray<T>::expand ( size_t amount ) [inline]

expand. Expand the number of array data slots by "amount" elements. Note that "array_size" is the total amount of storage available for data slots. "num_elem" is the number of data slots. The bounds over which the array can be indexed is governed by num_elem. Note that after expand() is called the new data elements can be read, but their value is undefined until they are initialized. Definition at line 179 of file grow_array.h. { bool allocOK = true; while (allocOK && num_elem + amount >= array_size) { allocOK = twice(); assert( allocOK ); } num_elem += amount; } // expand

template<class T> const T * GrowableArray<T>::getData ( ) const [inline]

Get a pointer to the internal data array. Definition at line 152 of file grow_array.h. { return pArray; }

template<class T> const size_t GrowableArray<T>::length ( void ) const [inline]

Length of the data (which is not necessarily the same as the length of the internal array. Definition at line 129 of file grow_array.h. Referenced by packfreq::plotMat(), and packfreq::prMat(). { return num_elem; }

template<class T> T GrowableArray<T>::operator[] ( const size_t i ) const [inline]

RHS [] operator. Definition at line 145 of file grow_array.h. { assert( i < num_elem ); return pArray[ i ]; }

template<class T> T & GrowableArray<T>::operator[] ( const size_t i ) [inline]

LHS [] operator. Definition at line 138 of file grow_array.h. { assert( i < num_elem ); return pArray[ i ]; }

template<class T> void GrowableArray<T>::remove ( void ) [inline]

Remove one item from the end of the array. Definition at line 192 of file grow_array.h. { if (num_elem > 0) num_elem--; }

template<class T> void GrowableArray<T>::set_to_zero ( ) [inline]

set array to zero length. Definition at line 132 of file grow_array.h. { num_elem = 0; }

template<class T> bool GrowableArray<T>::twice ( ) [inline, private]

twice. Double the amount of memory allocated for the array. Return true if memory allocation succeeded, false otherwise. Definition at line 86 of file grow_array.h. Referenced by append(), and expand(). { bool rslt; T *old_array = pArray; size_t new_size = array_size * 2; pArray = new T [ new_size ]; if (pArray != 0) { rslt = true; for (int i = 0; i < array_size; i++) { pArray[i] = old_array[i]; } delete [] old_array; array_size = new_size; } else { rslt = false; } return rslt; } // twice

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Member Data Documentation

template<class T> size_t GrowableArray<T>::array_size [private]

Array size (always <= num_elem). Definition at line 75 of file grow_array.h.

template<class T> size_t GrowableArray<T>::num_elem [private]

number of data elements. Definition at line 73 of file grow_array.h.

template<class T> T * GrowableArray<T>::pArray [private]

Definition at line 76 of file grow_array.h.

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The documentation for this class was generated from the following file:

• grow_array.h

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