Professor: Munehiro Fukuda

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CSS342 Template

• Professor Munehiro Fukuda

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Todays Topics

• Function templates
• Explained using a bubble sort example
• Class templates
• Explained using an insertion sort example
• Template compilation
• STL

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Function Templates
Function Templates

1. If you focus on just integers

1. If you use doubles instead

typedef double Object Object myMin( Object a,
Object b ) return ( a lt b ) ? a b int
main( ) cout ltlt myMin( 7.7, 5.5 ) ltlt endl
int myMin( int a, int b ) return ( a lt b ) ?
a b int main( ) cout ltlt myMin( 7, 5 )
ltlt endl

1. If you want to use both integers and doubles

template ltclass Objectgt Object myMin( Object a,
Object b ) return ( a lt b ) ? a b int
main( ) cout ltlt myMin( 7, 5 ) ltlt endl
cout ltlt myMin( 7.7, 5.5 ) ltlt endl
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Function Template Example 1Swap
Function Templates
int main( ) int x 5, y 7 double a 2,
b 4 string p "abc", q "xyz"
vectorltintgt v(5, 5), w(7, 7) mySwap( x, y )
cout ltlt x ltlt " " ltlt y ltlt endl mySwap( a, b
) cout ltlt a ltlt " " ltlt b ltlt endl mySwap( p,
q ) cout ltlt p ltlt " " ltlt q ltlt endl mySwap(
v, w ) for ( int i 0 i lt v.size( ) i )
cout ltlt vi for ( int i 0 i lt w.size( )
i ) cout ltlt wi cout ltlt endl
include ltiostreamgt include ltstringgt include
ltvectorgt using namespace std template ltclass
Objectgt void mySwap( Object lhs, Object rhs
) Object tmp lhs lhs rhs rhs
tmp
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Function Templates
Function Template Example 2Bubble Sort
Pass 1
Pass 2
Pass 3
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Pass 4
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Function Templates
Function Template Example 2Bubble Sort
(Continued)
include ltiostreamgt include ltvectorgt include
ltstringgt using namespace std template ltclass
Objectgt void bubbleSort( vectorltObjectgt a )
bool swapOccurred true // true when swaps
occur for ( int pass 1 ( pass lt a.size( ) )
swapOccurred pass ) swapOccurred
false // swaps have not occurred at the
beginning for ( int i 0 i lt a.size( ) -
pass i ) // a bubble(i) goes from 0 to
size - pass if ( ai gt ai 1 ) swap(
ai, ai 1 ) swapOccurred true // a swap
has occured
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Function Templates
Function Template Example 2Bubble Sort
(Continued)
int main( ) vectorltintgt intArray // The
integer array int x // An
integer to read cout ltlt "Enter positive
integers to sort ltlt endl while ( true )
cin gtgt x if ( x gt 0 )
intArray.push_back( x ) else break
bubbleSort( intArray )
vectorltstringgt strArray // The string array
string s // a string to read
cout ltlt "Enter strings to sort ltlt endl
while( cin gtgt s ) strArray.push_back( s )
bubbleSort( strArray ) cout ltlt "Sorted
strings are " ltlt endl for ( int i 0 i lt
strArray.size( ) i ) cout ltlt strArrayi
ltlt " " cout ltlt endl return 0
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Class Templates
Class Templates

• Private data members and a methods return value
  may be any class.
• Consider a sorted list whose item may be a string
  or an integer

class SortedList public void insert( const
string_or_int item ) const SortedList
operator( const SortedList rhs ) void
print( ) const private string_or_int array
void insertionSort( ) int main( )
SortedListltstringgt strList strList.insert(
abc ) SortedListltintgt intList
intList.insert( 5 )
Sorted
a
b
c
d
f
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b
c
d
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insert( )
Sorted
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insert( )
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How to Define the Template Header in .h (Sorted
List Example)
Class Templates
ifndef _SORTEDLIST_H_ define _SORTEDLIST_H_ in
clude ltiostreamgt include ltvectorgt using
namespace std templateltclass Objectgt class
SortedList public void insert( const Object
item ) const SortedListltObjectgt operator(
const SortedListltObjectgt rhs ) void print( )
const private vectorltObjectgt array void
insertionSort( ) include "SortedList.cpp
// discuss about this technique endif
At compilation time, Object will be replaced with
int or string
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How to Code the Template Implementation in .cpp
(Sorted List Example)
Class Templates
ifndef _SORTEDLIST_CPP_ define
_SORTEDLIST_CPP_ template ltclass Objectgt void
SortedListltObjectgtinsert( const Object item )
array.push_back( item ) // insert a new
item insertionSort( ) // sort
items template ltclass Objectgt const
SortedListltObjectgt SortedListltObjectgt operator
( const SortedListltObjectgt rhs ) //
concatenate two lists SortedListltObjectgt list
new SortedListltObjectgt list-gtarray
array for ( int i 0 i lt rhs.array.size( )
i ) list-gtarray.push_back( rhs.arrayi
) return list
At compilation time, Object will be replaced with
int or string
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How to Code the Template Implementation in .cpp
(Sorted List Example)
Class Templates
template ltclass Objectgt void SortedListltObjectgtp
rint( ) const // print out all sorted item
for ( int i 0 i lt array.size( ) i )
cout ltlt arrayi ltlt " " cout ltlt
endl template ltclass Objectgt void
SortedListltObjectgtinsertionSort( ) for (
int unsorted 1 unsorted lt array.size( )
unsorted ) // Assume the 0th item is
sorted. Unsorted items start from the 1st item
Object unsortedTop arrayunsorted // Copy
the top of unsorted group int i for ( i
unsorted - 1 ( i gt 0 ) (arrayi gt
unsortedTop ) --i ) // Upon a successful
comparison, shift arrayi to the right
arrayi 1 arrayi // insert the
unsorted top into the sorted group arrayi
1 unsortedTop endif
See the next slide for graphical explanation
unsortedTop
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insert
copy
compare
unsorted
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loc loc1
loc loc1
shift
loc loc1
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Insertion Sort
Class Templates
Sorted
Unsorted
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Copy 10
Shift 29
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Insert 10, copy 14
unsortedTop
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Shift 29
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Insert 14 copy 37
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Shift nothing
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Insert 37 Copy 13
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Shift 37, 29 and 14.
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Insert 13
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Tips for Template Compilation
Template Compilation

• You cannot compile SortedList.cpp independently.
• SortedList.cpp should be treated as if it were a
  part of a header file.
• SortedList.h at the end of this header file,
  add
• include SortedList.cpp
• SortedList.cpp at the beginning of this cpp
  file, do Not add
• include SortedList.h
• SortedListDriver.cpp
• Compile SortedListDriver.cpp only.
• In Eclipse, it is a bit tricky to exclude
  SortedList.cpp from compilation. To make it
  simple, we could name it as SortedList.cpp.h.

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Iterators
Standard Template Library

• A software design pattern that abstracts the
  process of scanning through a collection of
  elements
• The index of vector i can be considered as a
  primitive iterator which is however not enough
• The iterator should include
• The current position (like vectori)
• The retrieval of the current item (like
  vectori)
• The way of stepping to the next position (forward
  or backward)

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Vector and Iterators
Standard Template Library

• Vector has forward and reverse iterators

include ltiostreamgt include ltvectorgt using
namespace std int main( ) vectorltintgt
array for ( int i 0 i lt 10 i )
array.push_back( i ) vectorltintgtiterator f
// forward iterator for ( f array.begin( )
f ! array.end( ) f ) cout ltlt f ltlt
endl vectorltintgtreverse_iterator b //
reverse iterator for ( b array.rbegin( ) b
! array.rend( ) b ) cout ltlt b ltlt endl
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Standard Template Library
Standard Template Library

• Standard Template Library
• Provides typical templates such as vector, list,
  stack, and queue.
• At least, we have studied vector already.
• Containers
• Elements stored in STL template class
• Iterators
• A pointer to a container in operation.