Chapter 17 Templates

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Chapter 17 Templates
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Function Templates

• Express general form for a function
• Example template for adding two numbers

template ltclass Typegt Type sum (Type a, Type b)
return (a b)
Lesson 17.1
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Function Templates

• Called in same manner as ordinary function
• Permissible to have both generic data types and
  ordinary data types
• Treated similar to overloaded function
• Need to be careful that function call data types
  compatible with function bodies
• Useful for operations that apply to many data
  types

Lesson 17.1
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Overloaded Function Templates

• Cannot replace overloaded functions
• Perform same operations for each different data
  type
• Can vary number of arguments
• Specify more than one type of argument
• Distinguished by number or distribution of types
  of arguments

Lesson 17.1
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Class Templates Example
template ltclass Typegt class Class1
private Type value public
Class1 ( ) void
set_value (Type) Type get_value
( )
Lesson 17.2
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Class Template

• Allows creation of object of class and use the
  data type of choice
• Syntax to declare object
• Class1ltdoublegt ob
• Indicates the ob.value is type double

Lesson 17.2
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Mechanics of Class Templates

• Declaration for object using class template
• Causes memory reserved for all data members
• Causes instructions to be generated and stored
  for all function members
• If another object with same bracketed data type
  declared
• New memory reserved, but no new function
  instructions

Lesson 17.2
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Friends of Class Templates

• Four cases (assuming single type parameter)
• Ordinary function friend of each template class
  instantiated from class template
• Ordinary class friend of each template class
  instantiated from class template
• Template function only if type parameter for
  function and class same
• Template class only matching type class is
  friend

Lesson 17.2
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Sequence Containers
Standard Template Library

• Designed to directly control position of element
  within container
• Three containers
• vector
• deque
• list
• Dynamic memory allocation used to reserve memory

Lesson 17.3
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Vectors

• Need to include ltvectorgt header vector
  ltintgt vector1
• Declares vector1 to be vector container of int
• Elements in contiguous memory locations
• First element has subscript 0
• Can be accessed using array-like notation
• push family of functions reserve memory and
  initialize single element
• Random access

Lesson 17.3
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Deques

• Need to include ltdequegt header deque
  ltchargt deque1
• Declares deque1 to be deque container of char
• Can be created using push_front( ) and push_back
  ( )
• Elements in contiguous memory locations
• Can modify values with array notation
• First element, subscript 0
• Random Access

Lesson 17.3
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Lists

• Need to include the ltlistgt header list
  ltdoublegt list1
• Declares list1 to be list container of doubles
• Called doubly linked list
• Two pointer values one to next element and
  another to previous element
• Not stored in contiguous memory

Lesson 17.3
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Iterators
Standard Template Library

• Designed to be user-friendly pointers
• Know type of container
• Can go through list with operator
• General form for declaring container lttypegt
  iterator name
• ordinary iterator needs no special header file

Lesson 17.4
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Using an Iterator

• Need to initialize to point to location first
  then manipulate
• begin ( ) member function returns object that
  points to memory location of first element
• Can access element pointed to by iterator using
  unary operator

Lesson 17.4
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Constant Iterators

• General form or declaringcontainer lttypegt
  const_iterator name

Lesson 17.4
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List Iterators and Operators

• Called bidirectional iterators
• Cannot advance more than one element at a time
• Use both and - - to more forward and backward
  in list
• Useable operators
• unary operator, , --, , , and !

Lesson 17.4
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Algorithms
Standard Template Library

• Different definition than dictionary
• Global template functions designed to work with
  containers using iterators
• Not member functions
• called with function name and argument list
  name (iterator1, iterator2, iterator3)
• name is name of algorithm
• iterator1, iterator2, iterator3 names of
  iterators or return values from member functions

Lesson 17.5
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Summary

• Function templates
• Class templates
• Three types of sequences containers are vector,
  deque and list
• Basic components of STL are iterators, algorithms
  and containers
• STL has both sequence and associative containers