1. Type Conversions
Lecture 14
Wed, Feb 22, 2006

2. Topics Constructors as type converters Conversion operators 11/9/2018
Type Conversion

3. 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

4. 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

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

6. Example How would you convert a Point to a Vector? 11/9/2018
Type Conversion

7. 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

8. 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

9. Example: Convert Rational to float
Rational::operator float() const {
return (float)numerator/denominator; }
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Type Conversion