chapter 7 functions

Foundations of Engineering II- PVUHow to solve a big problem?3The Top-down design approach is based on dividingthe main probleminto smaller tasks which may be dividedinto simpler tasks,

Trang 1

TALENTS FOR DEVELOPMENT - Petrovietnam University

Chapter 7: Functions

Lecturer: Trần Ngọc Hiệp, MSc.

Email: hieptn@pvu.edu.vn Mobile: 0901 25 2468

Contents Functions

Advantages of functions Declaration and Defining a Function Function calling

Function Program Example

1

Trang 2

Trần Ngọc Hiệp, MSc Foundations of Engineering II- PVU

How to solve a big problem?

3

 The Top-down design approach is based on dividing

the main problem into smaller tasks which may be

divided into simpler tasks , then implementing each

simple task by a subprogram or a function

 This technique is called divide and conquer

7.1 Functions

 Function: A function is a group of statement that

together perform a specific task.

 Why use function: Function are used for divide a

large code into module due to this we can easily

debug an maintain the code.

4

3

4

Trang 3

7.2 Advantages of Functions

Functions separate the concept (what is done) from the implementation (how it is done).

Function make program easier to understand

Function can be called several times in the same program, allowing the code to be reused.

Avoid repeating of code

5

7.2 Advantages of Functions

Divide a complex problem into many simpler problems

Reduce chances of error

Makes modifying a program becomes easier

5

Trang 4

Types of Functions

Functions

Library Function of predefined Function

User defined Function

7

Types of Functions

8

 Library functions: are those which are predefined.

 Limitation of Library function:

 Contained limited task only

 Programmer do not have any controls on predefined

function.

 User Defined function: are created by programmer

according to their requirements.

7

8

Trang 5

Components of Function

Function prototype

Function definition Function call

9

7.3 Declaration and Defining a Function

1 Declaration and Defining:

Syntax:

9

Trang 6

7.3 Declaration and Defining a Function

 Return data type: A function may return a value

The return-data-type is the data type of the

values the function returns

 Function name: is the name of function.

 Parameters: This is a value which is pass in

function at the time of calling of function It is

optional.

 Function body: is the collection of statements.

11

Structure of a Function - Example

12

11

12

Trang 7

7.4 Function Calling

13

 In Calling program write the name of the function and provide

its arguments without data types.

 In calling a function, return value type and data types of the

arguments are not written.

The function can be called using either of the following methods

Call by

Value

Call by Reference

13

Trang 8

7.4 Function Calling - Call by Value

 In call by value mechanism, the called function

creates a new set of variables in stack and copies the

values of the arguments into them.

 In call by value method, the called function creates its

own copies of original values sent to it Any changes,

that are made, occur on the function’s copy of values

and are not reflected back to the calling function

 Arguments must be immutable objects

15

Trang 9

7.4 Function Calling - Call by Reference

 In call by reference mechanism, instead of passing

values to the function being called,

reference/pointers to the original variables are

passed

 In call by reference method, the called function

access and works with the original values using their

references Any changes , that occur, take place on the

original values are reflected back to the calling code.

 Argument must be mutable object such as List, Tuple,

Set, Dictionary

17

7.4 Function Calling - Call by Reference

 We also can pass the value by reference

 In this case we pass the address of the value rather

than value

 We use & operator for this purpose

 To call by reference we can’t pass value , we have pass

memory address of variable

Note: C++ passes arrays to functions by reference.

17

Trang 10

19

Call by Reference Example

Trang 11

Pass by Value Vs Pass by Reference

Pass by Reference Pass by Value

 Passes address of actual parameter

 Makes copy of actual

parameter

 Accesses original variable’s content

 Passes copy of contents

 Original variable’s content

 During program execution,

value parameter manipulates

data stored in own memory

overloading

Signature may be vary on the basis of number of argument or data type of argument or order of argument.

21

Trang 12

Function Overloading

23

 Syntax of Function Overloading:

Trang 13

Function Overloading

25

 Example: Overloading function by changing data type.

Default Arguments

 The default value for a parameter while declaring the

function is calling default argument.

 If we make a call to the function without passing any

value for that parameter, the function will take the

default value specified

 Example:

25

Trang 14

Default Arguments

 Rules for using default arguments:

 Only the last argument must be given default value

 If we default an argument, then you will have to default all

the subsequent arguments after that

 We can give any value a default value to argument

compatible with its datatype.

27

Nested Member Function of a Class

Nested member function

A member function can be called inside another member function of the same class is known as nesting

of member function.

28

27

28

Trang 15

7.5 Function Program Example

29

Problems Problem 1

• Write a program using function which accept two integers as an argument and return its sum.

Problem 2

• Write a function which calculates the raise to power of an input base number up to given power number.

Problem 3

• Write a program to show Prime numbers between two intervals by making used-defined Function.

29

Trang 16

Solutions

31

Problem 1:

Trang 17

Solutions

33

Problem 3:

Your Task

Write a program that lets the user perform arithmetic operations on two

number Your program must be menu driven, allowing the user to select the

operation (+,-,*, or /) and input the numbers Furthermore, your program

must consist of following functions:

• Function showChoice:

• Function add

• Function subtract

33

Trang 18

7.6 Variable Scope

 Variable Scope is a region of the program, where

variables can be declared:

 Inside a function: Local variables

 In the definition of function parameters: Formal

parameters

 Outside of functions: Global variables

35

Local variables

Formal parameters

Global variables

Trang 19

Trang 20

7.6 Variable Scope

39

Example of Global Variables

Trang 21

Python Standard Library

41

 Python Math

 Python has a set of built-in math functions,

including an extensive math module, that allows

you to perform mathematical tasks on numbers.

Python Math

41

Trang 22

Python Math

43

Python Math

44

43

44

Trang 23

Python Math

45

Python Standard Library

 Python Dates

 A date in Python is not a data type of its own, but

we can import a module named datetime to work

with dates as date objects.

45

Trang 24

Python Datetime

47

 To create a date.

Python Datetime

48

 The datetime object has a method for formatting

date objects into readable strings.

47

48

Trang 25

Python Datetime

49

Python Datetime

49

Trang 26

Python Datetime

51

Summary

52

1 • Function

2 • How to declared and defined a function

3 • Calling function by value

4 • Calling function by reference

5 • Variable scope

51

52

Trang 27

Quiz

53

Discussion

53

Trang 28

Trần Ngọc Hiệp, MSc Foundations of Engineering II- PVU 55

55

Tiêu đề	Functions
Người hướng dẫn	Trần Ngọc Hiệp, Msc.
Trường học	Petrovietnam University
Chuyên ngành	Foundations of Engineering II
Thể loại	lecture
Năm xuất bản	2024

Định dạng
Số trang	28
Dung lượng	2,05 MB