C Language Tips and Recursive Functions Examples

Creating a until(condition) loop in C as we seen in other languages


#define until(x)   while(!x)


/* on using until(x)  it will convert to  while(!x) */


#define NULL ((void*)0)


/* is the definition of NULL that points to a 0*/


#define EOF (-1)

/* the EOF macro constant */

A randum charector generating function



#include <stdlib.h>

#define randomChar() (rand() % 26 + 'a')



/* generages a randum lower case charecter */




#define FillCharArray(carray, arraySize) \

for(i=0; i < arraySize; i++) \

array[i]=randomChar();

/*A Macro to Print arrays of any primitive types..Macros will not do type checking, the control string for the printf() is given as argument */



#define printArray(array, elemntCount,controlString)

for(i=0; i < elemntCount; i++) \

printf(controlString,array[i]); \

putchar('\n')

/*We coud call this macro as : */


printarray(intArray, 10, "%-6d");




/* function to print bits of an int*/



void bitPrint(int x){


int i;


int n=sizeof(int) * CHAR_BIT; /* limits.h*/


int mask=1 << (n-1);


//putchar('\n');


for(i=1; i <=n;i++){

putchar( ((x & mask) == 0 )? 48 : 49);


x <<=1;


if(i % CHAR_BIT == 0)


   
putchar(' ');

}


/* to pack 4 charecters into an int and to unpack */



int pack(char a,char b,char c,char d){

int p=a;


p=(p << CHAR_BIT) | b;


p=(p << CHAR_BIT) | c;


p=(p << CHAR_BIT) | d;


return p;

}




char unpack(int p,int k){

int n=k*CHAR_BIT;


unsigned mask=255;


mask <<= n;


return ((p & mask ) >> n);

}



Resursive Functions


void printBack(char *str){

if(*str != 0)

printBack(str+1);

putchar(*str);

}



int fibonacci(int n){

if (n <= 1 )

return n;

else

return (fibonacci(n-1)+ fibonacci(n-2));

}