Templates

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Templates

• Andy Wang
• Data Structures, Algorithms, and Generic
  Programming

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Templates

• Provide generic programming
• Generic classes
• Generic functions
• Generic algorithms (later lectures)
• Goal
• Program reuse

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Motivating Example

• Find the largest element in an array
• int largest(const int iptr, unsigned int size)
• int current_largest iptr
• for ( size gt 0 --size, iptr)
• if (current_largest lt iptr)
• current_largest iptr
• return current_largest

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Motivating Example

• Find the largest element in an array
• float largest(const float iptr, unsigned int
  size)
• float current_largest iptr
• for ( size gt 0 --size, iptr)
• if (current_largest lt iptr)
• current_largest iptr
• return current_largest

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Motivating Example

• Find the largest element in an array
• double largest(const double iptr, unsigned int
  size)
• double current_largest iptr
• for ( size gt 0 --size, iptr)
• if (current_largest lt iptr)
• current_largest iptr
• return current_largest

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Motivating Example

• int int_array20
• float float_array30
• double double_array40
• cout ltlt largest(int_array, 20) ltlt ltlt
  largest(float_array, 30) ltlt ltlt
  largest(double_array, 40)

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Function Template Example

• Find the largest element in an array
• template lttypename Tgt
• T largest(const T iptr, unsigned int size)
• T current_largest iptr
• for ( size gt 0 --size, iptr)
• if (current_largest lt iptr)
• current_largest iptr
• return current_largest

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In-Class Exercise

• Swap two values of the same type

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Function Template Example 2

• Swap two values of the same type
• template lttypename Tgt
• void swap (T t1, T t2)
• T temp
• temp t1
• t1 t2
• t2 temp

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Class Template Example

• A class that holds a pair of items
• template lttypename Tgt
• class Pair
• public
• T first
• T second
• Pair()
• Pair(T t1, T t2)

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Class Template Example

• Constructors (in the same header file)
• template lttypename Tgt
• PairltTgtPair()
• template lttypename Tgt
• PairltTgtPair(T t1, T t2) first(t1), second(t2)
  

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Class Template Example

• Declarations
• Pairltintgt intPair(1, 2)
• Pairltfloatgt floatPair(1.1, 2.2)
• Pairlt Pairltintgt gt pair(intPair, intPair)

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Class Template Example 2

• A class that holds a pair of items with
  different types
• template lttypename T1, typename T2gt
• class Pair
• public
• T1 first
• T2 second
• Pair()
• Pair(T1 t1, T2 t2)

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Class Template Example 2

• Constructors
• template lttypename T1, typename T2gt
• PairltT1, T2gtPair()
• template lttypename T1, typename T2gt
• PairltT1, T2gtPair(T1 t1, T2 t2) first(t1),
  second(t2)

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Template Code Files

• Place template class definitions and
  implementation in the same header file
• Protect files from nested inclusions
• ifndef _YADDY_H
• define _YADDY_H
• endif _YADDY_H

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Next Two Class Meetings

• 9/15, 9/17
• MCH 201