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6

Functions

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Function Components

A function consists of function

prototype, function header and

function body.

Functions often require more than one

piece of information to perform their

tasks, which is passed by parameters.

Parameters are specified in both the

function prototype and the function

header.

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Function prototype

Also called a function declaration

Indicates to the compiler:

ame of the function

!ype of data returned by the function

Parameters the function e"pects to recei#e

!ypes of those parameters

$rder of those parameters

Example int max!int, int, int"

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Function %eader

&ame as function prototype but it also

includes the name of the parameters.

'"ample: int ma"(int ", int y, int )*

parameter names: ", y, )

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Function +ody

Function body beins with a left brace

followin the function header and ends

with a riht brace.

'": int ma"(int ", int y, int )*

- int ma"alue / "0

if ( y 1 ma"alue* ma"alue / y0 if( ) 1 ma"alue* ma"alue / )0

return ma"alue 2

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Function '"ecution

A function is in#oked by a function call

Followin a call, statements within thefunction body will e"ecute

'": ma" (rade3, rade4, rade5* arumets : rade3, rade4, rade5

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!hree ways to return control to the

callin statement

If the function does not return a result

( return type is #oid*:

Proram flow reaches the functionendin riht

brace or Proram e"ecutes the statement return;

If the function does return a result:

Proram e"ecutes the statement,

returnexpression; expressionis e#aluated and its #alue is returned to

the caller

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&torae Classes and &cope

Identifiers are used as #ariable andfunction names. Identifier properties,

Identifier7s storae class

8etermines the period durin which thatidentifier e"ists in memory

Identifier7s scope

8etermines where the identifier can bereferenced in a proram

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ariables

9ocal : !hese are #ariables defined

within a function. !hey will be #isible

only within the function. !hey e"ist only

durin the e"ecution of a function(e"ception static local #ariables*.

lobal: !hese are #ariables defined

outside of all the functions. !hey will be#isible in all the functions and they e"ist

durin the entire e"ecution.

7/23/2019 COEN 244 - 6 - Functions

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6.; Function Prototypes and Arument

Coercion (Cont.*

Function signature (or simply signature) The portion of a function prototype that includes the

name of the function and the types of its parameters

Does not specify the functions return type

Functions in the same scope must have unique

signatures

The scope of a function is the region of a programin which the function is known and accessible

7/23/2019 COEN 244 - 6 - Functions

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6.; Function Prototypes and Arument

Coercion (Cont.*

Argument oercion Forcing arguments to the appropriate types specified by

the corresponding parameters

For e!ample" calling a function with an integer argument"

even though the function prototype specifies a doubleargument

#!$ double sqrt( double !)

int ! % &'

sqrt( !)

The function will still work correctly

7/23/2019 COEN 244 - 6 - Functions

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'"plicit and Implicit Con#ersion between

data types

nary cast operator (e!plicit conversion) reates a temporary copy of its operand with a different data

type * #!ample$ int total % +

static_cast< double > ( total )

reates temporary floating,point copy of total Assignment operator( e!plicit conversion)

- Lower data type may be converted to

higher data type

Ex int x !"; double y; y ! x;- #igher data type may be converted to

lower data type

Ex int x; double y ! "$%; x ! y;

7/23/2019 COEN 244 - 6 - Functions

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Argument coercion occurs as if the argument value werebeing assigned directly to the parameter variable*

onverting a value to a lower fundamental type

-ill likely result in the loss of data or incorrect values

an only be performed e!plicitly

.y assigning the value to a variable of lower type (some

compilers will issue a warning in this case) or

.y using a cast operator

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/romotion (implicit conversion) onverting a value (e*g* int) to another data type (e*g*

double) to perform a calculation

00 /romotion 1ules

Apply to e!pressions containing values of two or more data

types

2uch e!pressions are also referred to as mi!ed,type

e!pressions

#ach value in the e!pression is promoted to the 3highest4type in the e!pression

Temporary version of each value is created and used for

the e!pression

5riginal values remain unchanged

1%

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Fi. 6.6< Promotion hierarchy for fundamental data types.

1&

7/23/2019 COEN 244 - 6 - Functions

16/222008 Pearson Education, Inc. All rights reserved.

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6.6 C== &tandard 9ibrary %eader Files

00 2tandard 6ibrary header files #ach contains a portion of the 2tandard 6ibrary

Function prototypes for the related functions

Definitions of various class types and functions

onstants needed by those functions

37nstruct4 the compiler on how to interface with library

and user,written components

8eader file names ending in $h

Are 3old,style4 header files

2uperseded by the 00 2tandard 6ibrary header files

1'

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Fi. 6.>< C== &tandard 9ibrary header files. (Part 3 of ?*

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7/23/2019 COEN 244 - 6 - Functions

18/222008 Pearson Education, Inc. All rights reserved.

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Fi. 6.>< C== &tandard 9ibrary header files. (Part 4 of ?*

1(

7/23/2019 COEN 244 - 6 - Functions

19/222008 Pearson Education, Inc. All rights reserved.

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Fi. 6.>< C== &tandard 9ibrary header files. (Part 5 of ?*

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7/23/2019 COEN 244 - 6 - Functions

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Fi. 6.>< C== &tandard 9ibrary header files. (Part ? of ?*

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)ath *i+rar -unctions

lobal functions

8o not belon to a particular class

%a#e function prototypes placed in header

files Can be reused in any proram that includes the

header file and that can link to the function7s

ob@ect code

'"ample: s&rtin header files&rt( '$ )

All functions in are lobal functions

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-ig. &.2 )ath li+rar /unctions.