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adding lecture 13 operators

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Jidong Xiao
2024-02-22 17:15:38 -05:00
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lectures/14_operators/README.md → lectures/13_operators/README.md
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@@ -1,10 +1,8 @@
# Announcements # Lecture 13 --- Operators & Friends
# Lecture 14 --- Operators & Friends
- Operators as non-member functions, as member functions, and as friend functions. - Operators as non-member functions, as member functions, and as friend functions.
## 14.1 Complex Numbers — A Brief Review ## 13.1 Complex Numbers — A Brief Review
- Complex numbers take the form z = a + bi, where i = √−1 and a and b are real. a is called the real part, b is called the imaginary part. - Complex numbers take the form z = a + bi, where i = √−1 and a and b are real. a is called the real part, b is called the imaginary part.
- If w = c + di, then - If w = c + di, then
@@ -13,7 +11,7 @@
– w × z = (ac − bd) + (ad + bc)i – w × z = (ac − bd) + (ad + bc)i
- The magnitude of a complex number is &radic;a<sup>2</sup> + b<sup>2</sup>; - The magnitude of a complex number is &radic;a<sup>2</sup> + b<sup>2</sup>;
## 14.2 Complex Class declaration ([complex.h](complex.h)) ## 13.2 Complex Class declaration ([complex.h](complex.h))
```cpp ```cpp
class Complex { class Complex {
@@ -36,7 +34,7 @@ Complex operator- (Complex const& left, Complex const& right); // non-member fun
ostream& operator<< (ostream& ostr, Complex const& c); // non-member function ostream& operator<< (ostream& ostr, Complex const& c); // non-member function
``` ```
## 14.3 Implementation of Complex Class ([complex.cpp](complex.cpp)) ## 13.3 Implementation of Complex Class ([complex.cpp](complex.cpp))
```cpp ```cpp
// Assignment operator // Assignment operator
@@ -72,7 +70,7 @@ ostream& operator<< (ostream & ostr, Complex const& c) {
} }
``` ```
## 14.4 Operators as Non-Member Functions and as Member Functions ## 13.4 Operators as Non-Member Functions and as Member Functions
- We have already written our own operators, especially **operator<**, to sort objects stored in STL containers. - We have already written our own operators, especially **operator<**, to sort objects stored in STL containers.
- We can write them as non-member functions (e.g., **operator-**). When implemented as a non-member function, - We can write them as non-member functions (e.g., **operator-**). When implemented as a non-member function,
@@ -91,7 +89,7 @@ Observe that the function has **only on**e argument!
objects. Calling constructors for **Complex** objects inside functions, especially member functions that work on objects. Calling constructors for **Complex** objects inside functions, especially member functions that work on
**Complex** objects, seems somewhat counter-intuitive at first, but it is common practice! **Complex** objects, seems somewhat counter-intuitive at first, but it is common practice!
## 14.5 Assignment Operators ## 13.5 Assignment Operators
- The assignment operator: **z1 = z2**; becomes a function call: **z1.operator=(z2)**; - The assignment operator: **z1 = z2**; becomes a function call: **z1.operator=(z2)**;
And cascaded assignments like: **z1 = z2 = z3**; are really: **z1 = (z2 = z3)**; And cascaded assignments like: **z1 = z2 = z3**; are really: **z1 = (z2 = z3)**;
@@ -104,7 +102,7 @@ The identifier this is reserved as a pointer inside class scope to the object wh
Therefore, ***this** is a a reference to this object. Therefore, ***this** is a a reference to this object.
- The fact that **operator=** returns a reference allows us to write code of the form: **(z1 = z2).real();** - The fact that **operator=** returns a reference allows us to write code of the form: **(z1 = z2).real();**
## 14.6 Exercise ## 13.6 Exercise
Write an operator+= as a member function of the Complex class. To do so, you must combine what you learned Write an operator+= as a member function of the Complex class. To do so, you must combine what you learned
about operator= and operator+. In particular, the new operator must return a reference, *this. about operator= and operator+. In particular, the new operator must return a reference, *this.
@@ -112,7 +110,7 @@ about operator= and operator+. In particular, the new operator must return a ref
## 14.7 Returning Objects vs. Returning References to Objects ## 13.7 Returning Objects vs. Returning References to Objects
- In the operator+ and operator- functions we create new Complex objects and simply return the new object. - In the operator+ and operator- functions we create new Complex objects and simply return the new object.
The return types of these operators are both Complex. The return types of these operators are both Complex.
@@ -128,7 +126,7 @@ This avoids creation of a new object.
created object! This results in someone having a pointer to stale memory. The pointer may behave correctly created object! This results in someone having a pointer to stale memory. The pointer may behave correctly
for a short while... until the memory under the pointer is allocated and used by someone else. for a short while... until the memory under the pointer is allocated and used by someone else.
## 14.8 Friend Classes vs. Friend Functions ## 13.8 Friend Classes vs. Friend Functions
- In the example below, the Foo class has designated the Bar to be a friend. This must be done in the public - In the example below, the Foo class has designated the Bar to be a friend. This must be done in the public
area of the declaration of Foo. area of the declaration of Foo.
@@ -146,7 +144,7 @@ contents) rather than Bar claiming it. What could go wrong if we allowed friends
grants these functions access similar to that of a member function. The most common example of this is grants these functions access similar to that of a member function. The most common example of this is
operators, and especially stream operators. operators, and especially stream operators.
## 14.9 Stream Operators as Friend Functions ## 13.9 Stream Operators as Friend Functions
- The operators >> and << are defined for the Complex class. These are binary operators. - The operators >> and << are defined for the Complex class. These are binary operators.
The compiler translates: cout << z3 into: operator<< (cout, z3) The compiler translates: cout << z3 into: operator<< (cout, z3)
@@ -159,7 +157,7 @@ function of the Complex class. This is why stream operators are never member fun
- Stream operators are either ordinary non-member functions (if the operators can do their work through the - Stream operators are either ordinary non-member functions (if the operators can do their work through the
public class interface) or friend functions (if they need non public access). public class interface) or friend functions (if they need non public access).
## 14.10 Summary of Operator Overloading in C++ ## 13.10 Summary of Operator Overloading in C++
- Unary operators that can be overloaded: + - * & ~ ! ++ -- -> ->* - Unary operators that can be overloaded: + - * & ~ ! ++ -- -> ->*
- Binary operators that can be overloaded: + - * / % ^ & | << >> += -= *= /= %= ^= - Binary operators that can be overloaded: + - * / % ^ & | << >> += -= *= /= %= ^=
@@ -176,7 +174,7 @@ operators in this order:
meaning of an operator. The whole point of operators is lost if you do. One (bad) example would be meaning of an operator. The whole point of operators is lost if you do. One (bad) example would be
defining the increment operator on a Complex number. defining the increment operator on a Complex number.
## 14.11 Extra Practice ## 13.11 Extra Practice
- Implement the following operators for the Complex class (or explain why they cannot or should not be - Implement the following operators for the Complex class (or explain why they cannot or should not be
implemented). Think about whether they should be non-member, member, or friend. implemented). Think about whether they should be non-member, member, or friend.

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lectures/14_operators/complex.h → lectures/13_operators/complex.h
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