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User-Defined Functions in C++ - Exercise 7, Slides of Computer Science

Biju Patnaik University of TechnologyComputer Science

The outline and tasks for exercise 7 in computer science 106, focusing on user-defined functions in c++. The exercise covers writing programs with user-defined functions, function headers, function bodies, function prototypes, return values, and passing variables to functions by value and reference. The tasks include using the getvalidint function and writing functions from pseudocode to compute maximum days in a month, determine if the year is a leap year, and get valid input on month, day and year.

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Exercise 7 -- Functions March 21-23, 2006
1
Exercise VII
Exercise VII –
–User
User-
-defined
defined
Functions
Functions
Larry Caretto
Computer Science 106
Computing in Engineering and
Science
March 21, 2006
2
Outline
• Exercise seven goals
• Outline tasks for exercise seven
• Provide details for task one
• Introduce task two
– Will discuss further on Thursday
• Exercise seven is linked to the first
programming project
– Functions developed in this exercise will be
used in project one
• Due date for exercise is April 4
3
Exercise Seven Goals
• As a result of this exercise you should
be able to accomplish the following:
– write programs with user-defined functions
• function header (with argument list)
• function body
• function prototype
– return values in function name
– pass variables to functions by value and by
reference
4
How do we write functions?
• C++ code is a collection of functions
• Each function, including main, has the
same level of importance
– Close code for each function before
starting a new function
int main()
{ // body of main
}
int myFunction( …… )
{ // body of myFunction
}
5
Use of Functions
• A function is designed to operate by
receiving data from a calling function
and returning results to that function
• Once a function is written, use it for
different applications by changing the
data in the call to the function
• You should not have to rewrite parts of
functions for different inputs
6
Tasks for Exercise Seven
•One –use of getValidInt function
– Provides utility that allows you to do data
validation for several int variables without
need to replicate code
•Two –write functions from pseudocode
to compute maximum days in a month,
determine if the year is a leap year, and
get valid input on month, day and year
– Routines will be used in first project
pf3
pf4
pf5

Partial preview of the text

Download User-Defined Functions in C++ - Exercise 7 and more Slides Computer Science in PDF only on Docsity!

Exercise VIIExercise VII – – User-User-defineddefined

FunctionsFunctions

Larry Caretto Computer Science 106

Computing in Engineering and

Science

March 21, 2006

2

Outline

  • Exercise seven goals
  • Outline tasks for exercise seven
  • Provide details for task one
  • Introduce task two
    • Will discuss further on Thursday
  • Exercise seven is linked to the first

programming project

  • Functions developed in this exercise will be used in project one
  • Due date for exercise is April 4

3

Exercise Seven Goals

  • As a result of this exercise you should

be able to accomplish the following:

  • write programs with user-defined functions
    • function header (with argument list)
    • function body
    • function prototype
  • return values in function name
  • pass variables to functions by value and by reference

4

How do we write functions?

  • C++ code is a collection of functions
  • Each function, including main, has the

same level of importance

  • Close code for each function before starting a new function int main() { // body of main } int myFunction( …… ) { // body of myFunction }

5

Use of Functions

  • A function is designed to operate by

receiving data from a calling function

and returning results to that function

  • Once a function is written, use it for

different applications by changing the

data in the call to the function

  • You should not have to rewrite parts of

functions for different inputs

6

Tasks for Exercise Seven

  • One – use of getValidInt function
    • Provides utility that allows you to do data validation for several int variables without need to replicate code
  • Two – write functions from pseudocode

to compute maximum days in a month,

determine if the year is a leap year, and

get valid input on month, day and year

  • Routines will be used in first project

7

Task One Functions

• main – you write this function to

get input using the getValidInt

function and write output

• getValidInt – copy this function from

the assignment

• Remember to write the function

prototype for getValidInt

8

getValidInt Function

  • Designed to provide simple approach to

obtaining integer input that is between

specified maximum and minimum value

  • Function parameters and minimum

value, maximum value, and string

description of parameter

  • Parameters passed to function by user
  • Function returns valid input through

function name

9

getValidInt

  • Function prototype

int getValidInt( int xMin, int xMax, string name );

  • This function returns a value for the integer

variable represented by the string, name,

that is between xMin and xMax

  • Example of use

int year = getValidInt( 1901, 2000,

“year from the twentieth century” );

10

What getValidInt Does

  • The function getValidInt( int xMin,

int xMax,string name ) does the

following tasks

  • Prompts the user for an input variable (named in the string passed in the third parameter) within a range defined by the first and second parameters
  • Gets the input from the user
  • Tells the user if there is an error and gets new input from the user in this case
  • Returns valid input to the calling function

11

Using getValidInt

  • The function getValidInt described

on the previous chart is used in exercise

seven and project one

  • Use #include
  • Examples of getValidInt use int month = getValidInt( 1, 12, “month”); int mayDay = getValidInt( 1, 31, “day of the month” ); int year = getValidInt( 1901, 2000, “year in the 20th century” );

12

Using getValidInt II

  • Examples of function use show different

variables are input by the same function

call

  • Only the data and the variable in which

the function result is returned change

  • Do not revise function code int month = getValidInt( 1, 12, “month”); int mayDay = getValidInt( 1, 31, “day of the month” );

Exercise VIIExercise VII – – User-User-defineddefined

FunctionsFunctions – – Day 2Day 2

Larry Caretto Computer Science 106

Computing in Engineering and

Science

March 23, 2006

20

Outline

  • Exercise seven goals
  • Summarize lecture material on functions
  • Outline tasks for exercise seven
  • Provide details for some tasks
  • Links between exercise seven and first

programming project

  • Exercise seven is due April 5 and

Project one is due April 7

21

Exercise Seven Goals

  • As a result of this exercise you should

be able to accomplish the following:

  • write programs with user-defined functions
    • function header (with argument list)
    • function body
    • function prototype
  • return values in function name
  • pass variables to functions by value and by reference

22

Function Example

bool leap( int year ) { if ( year % 4 != 0 ) return false; else if ( year % 400 == 0 ) return true; else if ( year % 100 == 0 ) return false; else return true; }

Header

Body

Name

Type

Argu- ment List (^) Multiple returns

23

Use of bool leap( int year )

bool leap ( year ); // prototype

int main() // examples of use

{ cout << “Enter a year: “;

int y; cin >> y; bool cond = leap( y ); if ( leap( y ) ) if ( leap( y ) && month == 2 )

24

Pass by Value and Reference

  • Pass by value is the normal operation
    • The value of the parameter in the calling code is passed to the function
    • If the corresponding dummy parameter in the function is changed, no change is made in the parameter in the calling code
  • Pass by reference is designated by

ampersand (&) in header

  • Parameter passed to function can be changed

25

Pass by

Value

// prototype int x2(int& x); // example of use int y = 5; cout << x2( y ) << “ “ << y //function int x2( int& x) { x = 2 * x; return x; } // output: 10 10

// prototype int x2(int x); // example of use int y = 5; cout << x2( y ) << “ “ << y; //function int x2( int x) { x = 2 * x; return x; } // output: 10 5

Pass by

Reference

26

Tasks for Exercise Seven

  • One – use of getValidInt function
    • Provides utility that allows you to do data validation for several int variables without need to replicate code
  • Two – write functions from pseudocode

to compute maximum days in a month,

determine if the year is a leap year, and

get valid input on month, day and year

  • Routines will be used in first project

27

Task One Functions

• main – you write this function to

get input using the getValidInt

function and write output

• getValidInt – copy this function from

the assignment

• Remember to write the function

prototype for getValidInt

28

Task Two Functions

  • main – you write this function that calls

the input function that you write

  • getMaxDays – write this function to get

maximum days in a month from

pseudocode in assignment

  • leap – write this function to tell if a year is

a leap year from pseudocode in

assignment

  • getValidInt – existing function from

task one

  • input – write this function that is similar

to main program from task one

29

getMaxDays

  • Function prototype

int getMaxDays( int month, int year );

  • This function returns the maximum number

of days in a month for an input month (1 to

12) and year.

  • Example of use

int mIn = 2, yIn = 2004;

int maxDays = getMaxDays( mIn, yIn );

30

leap

  • Function prototype bool leap( int year );
  • This function returns true or false if the

input year is or is not a leap year.

  • Example of use if( leap( year ) ) { cout << “February has 29 days”; }