1. Type Conversions
Lecture 13
Wed, Feb 21, 2007

2. Conversion of Types
Frequently in a program an object must be converted from one type to another.
For the built-in types, this is done automatically whenever it is sensible.
Convert float to int.
Convert int to float.
How can it be done with created types?
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Type Conversion

3. Converting to a Created Type
A class uses its constructors to define rules for converting an object of another type to an object of that type.
The prototype is
Class-name::Class-name(other type);
Rational::Rational(int);
Complex::Complex(double);
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Type Conversion

4. Example: Convert int to Rational
// Rational constructor
Rational::Rational(int n) {
numerator = n;
denominator = 1;
return; }
// Usages
Rational r(100);
Rational r = 100;
r = (Rational)100;
r = Rational(100);
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Type Conversion

5. Example How would you convert a Point to a Vector? vectr.h
VectrTest.cpp
point.h
point.cpp
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Type Conversion

6. Converting to a Built-in Type
Sometimes we want to convert an object of a created type to an object of a built-in type.
For example, we might want to convert
A Rational to a float.
A Complex to a double.
For this we need a conversion operator.
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Type Conversion

7. Conversion Operators A conversion operator has prototype
The operator converts the created-type object to the built-in type and returns the object of the built-in type.
Class-name::operator built-in-type() const;
Rational::operator float() const;
Complex::operator double() const;
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Type Conversion

8. Example: Convert Rational to float
Rational::operator float() const {
return (float)numerator/denominator; }
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9. Convert a Rational to a Float
rational.h
rational.cpp
RationalTest.cpp
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Type Conversion