Aae oop xp_06

More About Functions

Objectives
In this lesson, you will learn to:
Use in-built functions in a program
Handle command line parameter in a program
Handle pointer to functions

©NIIT OOPS/Lesson 6/Slide 1 of 16


In-Built Functions
C++ provides predefined functions to manipulate
string and numeric data
Some of the in-built string functions are:
strcpy- copies the contents of the second string to
the first string. The syntax is as follows:
char * strcpy ( char * dest, const char * src );
For example, strcpy(cStr1,“Judas Priest”);
strcat- is used to join (concatenate) the second
string with the first string. The syntax is as follows:
char * strcat ( char * dest, const char * src );
For example, strcat(cStr1, “ABC”);


In-Built Functions (Contd..)
strncpy- Copies the specified number of characters
of the second string to the first string. The syntax is
as follows:
char * strncpy ( char * dest, const char * src, sizet_t
num );
For example, strcpy(cStr1,“Judas
Priest”,5);
strlen- Returns the length for the string. The syntax
is as follows:
size_t strlen ( const char * str1 );
For example, iNum=strlen(cStr1);



strstr- Scans string1 for the first occurrence of
string2. The syntax is as follows:
Char * strstr (char * string1, const char * string2 );
For example, char str1[]=”Hello World”;
char str2[]=”or”;
char * sFound=strstr(str1,str2);
coutsFound-str1+1;
strcmp- compares two strings (supplied as its
parameters) and returns an integer value.



The syntax is as follows:
Char * strstr (char * string1, char * string2 );
For example,
iNum=strcmp(“madonna”,”maradona”);
strchr- Searches for a character in a string. The
syntax is as follows:
char * strchr ( const char * string, int c );
For example, ptr = strchr( s, '0' );



Some of the in-built numeric functions are:
abs- Returns absolute value of the integer
parameter. The syntax is as follows:
int abs ( int n );
For example, abs(-2)
ceil- Rounds up the parameter to the nearest
integer value. The syntax is as follows:
int ceil ( int n );
For example, ceil(1.4)



floor- Returns the largest integer that is less than
or equal to the integer passed as a parameter. The
double floor ( double x );
For example, floor(1.8)
sqrt- Returns the square root of parameter. The
double sqrt ( double x );
For example, param = 1024.0;
result = sqrt (param);



atoi- Returns the integer value stored as a string.
The syntax is as follows:
int atoi (const char * string)
For example, char str[]=”345A”;
result=atoi(str);



Command Line Parameters
Command line parameters are the values are passed
from the command prompt to the program during
program execution.
The two parameters of the C++ main() function that
interpret the values are:
argc
argv



Declaration of Functions
The syntax to declare a function is as follows:
void main(int argc, char *argv[])
{
}



Problem Statement 6.D.1
Write a program, which accepts five numbers from
command line and display it.



Just a Minute…
int argc gives ________________
char *argv[] gives ________________.



Problem Statement 6.P.1
Modify the existing empsalary module of Diaz
Telecommunication Inc. to increment the salary of
their employees. Increment amount need to be
passed from command line.



Pointer to Function
Function pointers are pointers, i.e. variables, which
point to the address of a function.
The addresses that the function pointers contain
reside in the code segment itself
The syntax to declare to declare a function pointer is
as follows:
[return_type] (*pointer_name)[(list_of_parameters)]
A pointer to a function can be initialized with the name
of a function, within the declaration of the pointer. For
example,
long max(const long* array,int cnt); pFun=max;



Summary
In this lesson, you learned that:
C++ provides several in-built functions.
Some of the commonly used string functions are:
strcpy
strcat
strncpy
strlen
strstr
strcmp
strchr


Summary (Contd..)
Some of the commonly used numeric functions are:
floor
ceil
abs
Sqrt
Command line parameters add functionality to your
programs by allowing you to pass parameters with
your C++ program.
Function pointers are pointers, i.e. variables, which
point to the address of a function.


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