Can anybody show me why this works??

This is a discussion on Can anybody show me why this works?? within the C Programming forums, part of the General Programming Boards category; I found this recursive function code in a C book. I do not understand why it works. It seems to ...

  1. #1
    Registered User
    Join Date
    Mar 2008
    Posts
    6

    Can anybody show me why this works??

    I found this recursive function code in a C book. I do not understand why it works. It seems to me that there is no variable in the function the keep up with the results, yet it works perfectly! Just curious.

    Thanks to anyone who can trace this program and show me what it is doing that I cannot see.

    tzuch

    Code:
    #include <stdio.h>
    
    int three_powered(int power);
    
    main(void)
    {
    	int a=0, fin;
    
    	puts("Enter an exponent:  ");
    	scanf("%d", &a);
    	
    	
    	printf("\n3 to the power of %d is %d",a,three_powered(a) );
    
    	puts("\n\nEnter a digit...");
    	scanf("%d", &fin);
    
    	return 0;
    
    }
    
    int three_powered(int power)
    {
    	if(power<1)
    	{
    		return 1;
    	}
    	
    	else
    	{
    		return(3*three_powered(power-1));
    	}
    }

  2. #2
    CSharpener vart's Avatar
    Join Date
    Oct 2006
    Location
    Rishon LeZion, Israel
    Posts
    6,452
    I have added some traces for your convinience... hope they will help you to understand what is going on
    Code:
    #include <stdio.h>
    
    int three_powered(int power);
    
    int main(void)
    {
    	int a=0, fin;
    
    	puts("Enter an exponent:  ");
    	scanf("&#37;d", &a);
    	
    	
    	printf("\n3 to the power of %d is %d",a,three_powered(a) );
    
    	puts("\n\nEnter a digit...");
    	scanf("%d", &fin);
    
    	return 0;
    
    }
    
    int three_powered(int power)
    {
    	if(power<1)
    	{
    		printf ("3^0 == 1\n");
    		return 1;
    	}
    	else
    	{
    		int res  = 3*three_powered(power-1);
    		printf ("3^%d == %d\n", power, res);
    		return(res);
    	}
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
    Registered User
    Join Date
    Mar 2008
    Posts
    6
    thank you very much vart. I should have done that but I'm fairly new at this.

    tzuch

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