Linux C Function Practice __oracle

Learning function is mainly to learn the function of the declaration, definition and invocation, see the following two examples to help us learn functions:

Topic One:

Write a function Iswithin () that accepts two arguments, one is a character, and the other is a string pointer. Its function is if the character is in a string. Returns 1 (true), or 0 (false) if the character is not in the string. Test in a complete program that uses circular statements to provide comfort for this function.

The code is as follows:

#include <stdio.h>

int iswithin (char p,char *q)
{while
	(*q)
	{
		if (p = = *q) return
			1;
		else
			q++;
	}
			return 0;
}
int main (int argc, char *argv[])
{
	int m;
	char p,*q;
	p = *argv[1];
	Q = argv[2];

	m = Iswithin (p,q);

	if (m = = 1)
		printf ("\ '%c\ ' is in the string!\n", p);
	else
		printf ("\ '%c\ ' isn't in" string!\n ", p);

	return 0;
}

The results of the implementation are as follows:

fs@ubuntu:~/qiang/hanshu$./hanshu2 h Hello
' h ' is in the string!
fs@ubuntu:~/qiang/hanshu$/hanshu2 H World
' H ' isn't in the string!
fs@ubuntu:~/qiang/hanshu$ 

Notice how the function passes the argument.

Topic Two,

the function of the following function is to compute the value of the N-Order de-phasor of X by a recursive method. An existing Call statement P (n,x): Write function implementation functionality.

The code is as follows:

#include <stdio.h>

int p (int n,int x)
{
	int m;

	if (n = = 0) return
		0;
	else
		if (n = = 1) return
			x;
		else
		{
			m = ((2*n-1) *x*p (n-1,x)-(n-1) *p (n-2,x))/n;
			return m;
		}
}

int main (int argc, const char *argv[])
{
	int x, n;
	int q;
	printf ("Please input x and n:\n");
	scanf ("%d%d", &x,&n);
	Q = P (n,x);

	printf ("p =%d\n", q);

	return 0;
}

The results of the implementation are as follows:

fs@ubuntu:~/qiang/hanshu$./HANSHU1 please
input x and N:
2
1
p = 2
Fs@ubuntu:~/qiang/hanshu $./HANSHU1 please
input x and N:
2 
5
p = 194
fs@ubuntu:~/qiang/hanshu$