Department of Computer and Information Science, School of Science, IUPUI Fall 2003

1
Department of Computer and Information
Science,School of Science, IUPUIFall 2003
Templates

• Dale Roberts, Lecturer
• Computer Science, IUPUI
• E-mail droberts_at_cs.iupui.edu

2
Templates

• A Template Defines the Content of a Family of
  Data Types
• Two Types -- Function and Class Templates

3
Function Templates

• Specifies a Generic Class and Uses this Class in
  the Function Algorithm
• Compiler Creates Appropriate Function Definition
  Using the Argument Specified During a Function
  Call Invocation

4
Function Template -- Example

• includeltstream.hgt
• //Template Function Definition
• template ltclass Tgt T maximum(T t1, T t2)
• if (t1 gt t2) return t1
• else return t2
• main()
• int a 10, b 15
• float c 20.0, d 25.5
• cout ltlt "Maximum Integer " ltlt maximum(a, b)
  ltlt endl
• cout ltlt "Maximum Float " ltlt maximum(c, d) ltlt
  endl
• //ERROR....Parameter Type Mismatch -- No
  Conversion
• cout ltlt "Maximum " ltlt maximum(a, d) ltlt endl
• //Explicit Prototype for Forced Conversion
• float maximum(float, float)

5
Class Template

• Specifies a Generic Class and Uses it in the
  Algorithm
• Proper Arguments Must be Supplied Before Creating
  an Instance (or Object) Using the Template Class

6
Class Template -- Stack Example

• //A Stack of Arbitrary Elements
• template ltclass Tgt class stack
• T head
• T tail
• int sz
• public
• stack(int s)head tail new Tsz s
• stack()delete head
• void push(T a) tail a
• T pop() return --tail
• int size() const return tail - head
• main()
• //Stack of 100 Characters
• stackltchargt char_stack(100)
• char_stack.push('R')
• cout ltlt "Stack Size " ltlt char_stack.size()
  ltlt endl

7
Class Template -- Stack Example -- Cont'd

• OUTPUT WILL BE
• ------ ---- --
• Stack Size 1
• Top 10

8
Container Classes

• Useful Kind of Classes
• These Hold Objects of Some Other Type
• Examples -- Lists, Arrays, Sets
• A Set can Contain
• Integers
• Characters
• Floats
• Strings
• Structures Representing Citizens

9
Properties of Container Classes

• The type of the objects that they hold is of
  little importance to the definer of the
  container, but of crucial Importance to the user
  of a particular container
• For the definer, the behavior of the Container
  Class is important
• The type of the object is treated as an argument
  by the Definer and is specified by the User