Lecture 28 - C++ Inheritance&Overloading - 06

8/20/2019 Lecture 28 - C++ Inheritance&Overloading - 06

1/21

Lect 28

Engineering H192 - Computer Programming

Winter Quarter The Ohio State University

Gateway Engineering Eduation Coa!ition

"nheritane and Over!oading

#eture 2$


2/21

Lect 28




"nheritane

• O%&ets are o'ten de'ined in terms o' hierarhia!!asses with a %ase !ass and one or more !eve!so' !asses that inherit 'rom the !asses that area%ove it in the hierarhy(

• )or instane* graphis o%&ets might %e de'ined as'o!!ows+


3/21

Lect 28




"nheritane ,ontinued

• This hierarhy ou!d* o' ourse* %e ontinued 'or more

!eve!s(

• Eah !eve! inherits the attri%utes o' the a%ove !eve!( Shape

is the %ase !ass( 2-. and /-. are derived 'rom Shape andCir!e* S0uare* and Triang!e are derived 'rom 2-.( Simi!ar!y*

Sphere* Cu%e* and Tetrahedron are derived 'rom /-.(


4/21

Lect 28





!ass A + %ase !ass aess spei'ier B

mem%er aess spei'ier,s+

(((mem%er data and mem%er 'untion,s

(((

3

4a!id aess spei'iers in!ude pu%!i* private* and

proteted


5/21

Lect 28




Pu%!i "nheritane

pu%!i %ase !ass ,5

public membersprotected members

private members

derived !ass ,6

publicprotected

inherited but not

accessible

!ass A + pu%!i B

// Class A now inherits the members of Class B

// with no change in the “access specifier” for

3 // the inherited members


6/21

Lect 28




Proteted "nheritane

proteted %ase !ass ,5


private members

derived !ass ,6

protectedprotected

inherited but not

accessible

!ass A + proteted B


// with pu%!i members “promoted” to proteted

3 // but no other changes to the inherited members


7/21

Lect 28




Private "nheritane

private %ase !ass ,5


private members

derived !ass ,6

privateprivate

inherited but not

accessible

!ass A + private B


// with pu%!i and proteted members

3 // “promoted” to private


8/21

Lect 28




"nheritane ,ontinued!ass Shape

pu%!i+

int GetColor ,

proteted+ // so derived classes can access it

int color 3

!ass Two! + pu%!i Shape

// put members specific to "! shapes here

3

!ass Three! + pu%!i Shape

// put members specific to #! shapes here

3


9/21

Lect 28





!ass S$uare + pu%!i Two!

pu%!i+

'!oat getArea ,

proteted+

'!oat edgelength

3

!ass Cube + pu%!i Three!

pu%!i+

'!oat get%olume ,

proteted+

'!oat edgelength

3


10/21

Lect 28





int main ,

S$uare m&S$uare

Cube m&Cube

m&S$uare(getColor , // S$uare inherits getColor'(

m&S$uare(getArea ,

m&Cube(getColor , // Cube inherits getColor'(

m&Cube(get%olume ,

3


11/21

Lect 28




)untion Over!oading

• C77 supports writing more than one 'untion with

the same name %ut di''erent argument !ists( This

ou!d in!ude+

) di''erent data types

) di''erent num%er o' arguments

• The advantage is that the same apparent 'untion

an %e a!!ed to per'orm simi!ar %ut di''erenttas8s( The 'o!!owing wi!! show an eamp!e o'

this(


12/21

Lect 28




)untion Over!oading

void swap ,int *a+ int *b

void swap ,'!oat *c+ '!oat *d

void swap ,har *p+ har *$

int main ,

int a , -+ b , .

'!oat c , .01+ d , 21034

har p , 565 + $ , 5n5

swap ,7a+ 7b

swap ,7c+ 7d

swap ,7p+ 7$

3


13/21

Lect 28




)untion Over!oading

void swap ,int *a+ int *b

int temp temp , *a *a , *b *b , temp 3

void swap ,'!oat *c+ '!oat *d

'!oat temp temp , *c *c , *d *d , temp 3

void swap ,har *p+ har *$ har temp temp , *p *p , *$ *$ , temp 3


14/21

Lect 28




)untion Temp!ates

• :e have disussed over!oaded 'untions as a way

to per'orm simi!ar operations on data o' di''erent

types( The swap 'untions were an eamp!e(

• :e wrote three 'untions with the same name %ut

di''erent data types to per'orm the swap

operations( Then we ou!d a!! swap ,;a* ;%* 'or

eamp!e* and C77 wou!d se!et whih 'untion touse %y mathing the data type o' a and % to one o'

the 'untions(


15/21

Lect 28




)untion Temp!ates

• 6nother way to per'orm this tas8 wou!d %e to

reate a function template de'inition(

• :ith a function template de'ined* when we a!!

swap ,;a* ;%* C77 wi!! generate the o%&et ode

'untions 'or us( The program on the 'o!!owings!ides is an eamp!e(


16/21

Lect 28




)untion Temp!ates

temp!ate


17/21

Lect 28




)untion Temp!ates

int main ,

int a , :+ b , .

'!oat c , 10.+ d , 403

har e , 565+ f , 5;5 swap ,7a+ 7b // compiler puts int in for T

swap ,7c+ 7d // compiler puts float in for T

swap ,7e+ 7f // compiler puts char in for T

out


18/21

Lect 28




Operator Over!oading

• C77 a!ready has a num%er o' types ,e(g(* int* '!oat*

har* et( that eah have a num%er o' %ui!t in

operators( )or eamp!e* a float an %e added to

another float and stored in yet another float with

use o' the 7 and > operators+'!oatC > '!oat6 7 '!oat5

• "n this statement* '!oat5 is passed to '!oat6 %y

way o' the 7 operator( The 7 operator 'rom '!oat6

then generates another float that is passed to'!oatC via the > operator( That new float is then

stored in '!oatC %y some method out!ined in the >

'untion(


19/21

Lect 28




Operator Over!oading ,ontinued

• Operator over!oading means that the operators+

) Have mu!tip!e de'initions that are

distinguished %y the types o' their parameters*and

) :hen the operator is used* the C77 ompi!er

uses the types o' the operands to determinewhih de'inition shou!d %e used(


20/21

Lect 28





• 6 programmer has the a%i!ity to re-de'ine or hange how

the operators ,7* -* ?* @* >*


21/21

Lect 28





Steps 'or de'ining an over!oaded operator+

1( Aame the operator %eing over!oaded(

2( Spei'y the ,new types o' parameters ,operands

the operator is to reeive(

/( Spei'y the type o' va!ue returned %y theoperator(

B( Spei'y what ation the operator is to per'orm(

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Lecture 28 - C++ Inheritance&Overloading - 06