LECTURE 19

Results of Mixed Arithmetic Expressions

float f_value ;

double d_value ;

char c_value ;

short int s_value ;

long int l_value ;

int i_value ;

Expression	Type
c_value * i_value	int
f_value - 7.3	double
d_value + c_value	double
c_value - s_value	int
s_value - l_value	long int
s_value + 7	int
s_value - 7.0	double
7 + 7.0	double

Example Use of Casts

double ratio, q, r ;

q = 7.0 ;

r = 2.0 ;

ratio = (int) q / (int) r ;

String Functions

Functions	Arguments	Description
strcpy( )	char *s1, char *s2	copies s2 to s1 ; returns s1
strncpy( )	char *s1, char *s2, int n	copies at most n characters of s2 to s1 ; returns s1
strcat( )	char *s1, char *s2	concatenates s2 to end of s1 ; returns s1
strncat( )	char *s1, char *s2, int n	concatenates first n characters of s2 to end of s1 ; returns s1
strcmp( )	char *s1, char *s2	compares s1 to s2 ; returns < 0 if s1 < s2, 0 if s1 == s2 or > 0 if s1 > s2
strlen( )	char *s1	returns length of s1 ( not including `\0` )

Program Using String Functions

/* test various functions in string library */
#include <stdio.h>
#include <string.h>

main ( )
{

   char string1[ ] = ''document'' ; /* first test string */
   char string2[ ] = ''disk'' ; /* second test string */
   char s3[20], s4 [20], s5[20] ;

   /* test string length */
   printf(''Length of string 1 is %d\n'', strlen(string1)) ;

   /* test string copy functions */
   strcpy(s3, string2) ;
   strncpy(s4, string2, 3) ;
   printf(''Two copied strings are %s and %s \n'', s3, s4) ;

   /* test string concatenation functions */
   strcat(s3, string1) ;
   strncat(s4, string1, 3) ;
   printf(''Two concatenated strings are %s and %s \n'', s3, s4) ;

   /* test string comparison */
   if(strcmp(s3, s4)) printf(''Strings are different \n'') ;
   else 
      printf(''Strings are identical \n'') ;
}

OUTPUT :

Length of string1 is 8
Two copied strings are disk and dis
Two concatenated strings are disk document and disdoc
Strings are different

Function to Compute Length of a Vector

/* function to compute the length of a vector */

#include <math.h>
double length( double v[ ], int n)
{
   double total = 0.0 ;
   int i ;
   for( i=0 ; i<n ; i++ ) total += v[i] * v[i] ;
   return(sqrt(total)) ;
}

Function to Compute Inner Product of Two Vectors

/* function to compute an inner product */

double inner_product( double v[ ], double w[ ], int n )
{
   double total = 0.0 ;
   int i ;
   for ( i=0 ; i<n ; i++ ) total += v[i] * w[i] ;
   return(total) ;
} 

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