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Operator Overloads Part1
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Rational Class RationalNumber (Fraction) class: Rational
-numerator: int -denominator: int +Rational(numerator: int, denominator: int) +getNumerator(): int const +getDenominator(): int const +add(secondRational: Rational&): Rational const +subtract(secondRational: Rational&): Rational const +multiply(secondRational: Rational&): Rational const +divide(secondRational: Rational&): Rational const +compareTo(secondRational: Rational&): int const +equals(secondRational: Rational&): bool const +intValue(): int const +doubleValue(): double const +toString(): string const -gcd(n: int, d: int): int
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Rational Use Currently awkward to use:
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Rational Use What we want:
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Operator Overloading Classes get = and . operators automatically
May need to change = Can overload other operators + - / * == > etc… Can't Make new operators Change precedence Change how operators work on plain types
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Overload as Member Overload as member function:
r1 + r2 interpreted as r1.operator+(r2)
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Overload as Member Implemented as member function:
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Notes Parameter can be any type:
Return type doesn't have to be same class:
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Other Overloads Other math as members:
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Other Overloads Relational as members:
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Relational Implementation
Compare this to other, return true or false
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Unary Unary operators
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Augmented Assignments
Expected to change original Expected to return a reference to original object
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Augmented Assignment Augmented assignments return current object as reference
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Augmented Assignment Augmented assignments return current object as reference r3 numerator 1 denominator 3
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Augmented Assignment Augmented assignments return current object as reference r3 numerator 11 denominator 15
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Augmented Assignment Augmented assignments return current object as reference r3 r3 numerator 11 denominator 15
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Augmented Assignment Augmented assignments return current object as reference r3 r3 numerator 63 denominator 45
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Augmented Assignment Augmented assignments return current object as reference r3 r3 numerator 63 denominator 45
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++i vs i++ Preincrement Postincrement int x = 10; int y = ++x; x = 11
Change x, use new value Copy x to use in rest of statement, change x
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Pre-crements Preincrement/decrement Operator ++ or --
Return reference to original
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Pre behavior Preincrement in action: r2 numerator 2 denominator 3
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Pre behavior Preincrement in action: r2 numerator 5 denominator 3
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Pre behavior Preincrement in action: r2 r2 numerator 5 denominator 3
temp numerator 5 denominator 3
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Post-crements Postincrement/decrement
Dummy int param to distinguish pre/post Don't use Return a new object with old value
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Post behavior Postincrement in action: r2 numerator 2 denominator 3
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Post behavior Postincrement in action: r2 numerator 2 denominator 3
temp numerator 2 denominator 3
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Post behavior Postincrement in action: r2 numerator 5 denominator 3
temp numerator 2 denominator 3
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Post behavior Postincrement in action: temp r2 numerator 5 denominator
3 temp2 numerator 2 denominator 3 temp numerator 2 denominator 3
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Post behavior Postincrement in action: r2 numerator 5 denominator 3
temp2 numerator 2 denominator 3
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Important Lesson x++ generally involves copy for objects
Favor ++x over x++ for objects
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