Chapter 123 Discovering C

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Chapter 12-3Discovering C
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Polymorphism

• Indicates that the same word or symbol can have
  different meanings
• overloading function names, overloading
  operators, and templates
• Function name overloading
• ex) Constructors
• The same functions have different parameter lists
• During compilation, the compiler inspect the
  number and type of the actual parameters

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Operator overloading

• Allows operator symbols to have different
  meanings with different types
• ex) ltlt
• integer bitwise left shift
• takes an ostream object as its left operand and
  either a string or one of the fundamental types
  as its right operand
• gtgt
• Most operators in C can be overloaded.

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Operator overloading (II)

• In C, operator is regarded as a function
• ex) for operator _at_
• the function name is operator_at_
• parameters are the left and right data of the _at_
• int result, a, b
• result ab //result operator(a,b)
• Overloading operators is done in the context of
  classes
• At least one of the operands of an overloaded
  operator must be of a class type
• Unary operator
• ex) result _at_data
• result data_at_
• MyClass operator_at_(MyClass data)

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Operator overloading (III)

• class Complex
• private
• float real, imag
• public
• Complex()realimag0
• Complex(int r, int i) realr imagi
• Complex operator-()
• friend Complex operator(Complex c)
• Complex Complexoperator-()
• Compex c
• c.real-real
• c.imag-imag
• return c
• Complex operator(Complex c1)
• Complex c2
• c2.realc1.real
• c2.imag-c1.imag

Complex c1, c2(1,5) //c100i, c215i c1-c2
//c1-1-5i //c1c2.operator-() c1c2
//c11-5i //c1operator-(c2)
this
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Operator overloading (IV)

• class Complex
• ....
• public
• ....
• Complex operator(Complex c)
• friend Complex operator-(Complex c1, Complex
  c2)
• Complex Complexoperator(Complex c)
• Complex c3
• c3.realrealc.real
• c3.imagimagc.imag
• return c3
• Complex operator-(Complex c1, Complex c2)
• Complex c3
• c3.realc1.realc2.real
• c3.imagc1.imagc2.imag
• return c3

Complex comp1,comp2,comp3 .... comp3comp1comp2
//comp3comp1.operator( comp2) comp3comp1-co
mp2 //comp3operator-(comp1,comp2)
this