Recursive Function equation

Forewarning, this is a homework assignment.
I am supposed to create a recursive function but I am doing this wrong. When I enter a 4 I am supposed to get a result of 16 from f(x) but I get -2. I don't really understand where I went wrong. Also I don't know if I am supposed to print my results inside of main or in f.

Write a program that queries the user for an integer value and uses a recursive

function that returns the value of the following recursive definition:

f(x) =x+3 if x <=0



f(x)=f(x-3)+(x+5) otherwise

My attempt:

#include <stdio.h>

int f(int x); //Prototype to call to f



int main(void) {

  int n; //number the user will input



//Ask user to input data an reads it

  printf("Enter a whole number: ");

  scanf("%d", &n);



//Pointer for f

  f(n);



//Prints results

  printf("nn is %dn", n);

  printf("f(x) is %dn", f(n));

  return 0;

}



int f(int x) {

//Checks if equal to zero

  if (x <= 0) {

     x + 3;

  }

//If not equal to zero then do this

  else {

     f(x - 3) + (x + 5);

  }

}

Thank you all for the help, learned a lot from your comments and suggestions.
I was able to get it work I believe https://pastebin.com/v9cZHvy0

edited Nov 28 '18 at 4:51

asked Nov 28 '18 at 4:03

Alec Mauro

Every recursive function has (1) an exit condition, and (2) a recursive call. You provide no exit condition. Further, you need scanf("%d", &n) (note the '&') and you must validate the return, e.g. if (scanf("%d", &n) != 1) { /* handle error */ }. Your call to f(n); is not a // Pointer for f it is simply a function call (that makes little sense there). Think through how your set of recursive calls must exit. As it is the computation of (x-3)+(x+5) grows in size so x <= 0 cannot be the exit condition.

– David C. Rankin
Nov 28 '18 at 4:33

@DavidC.Rankin: The exit condition is x <= 0. It seems you may have missed the fact that f(x-3) calls f and (x+5) does not.

– Eric Postpischil
Nov 28 '18 at 4:36

Yes, I read it as f (x-3 + x + 5).

– David C. Rankin
Nov 28 '18 at 4:37

add a comment |

Write a program that queries the user for an integer value and uses a recursive

function that returns the value of the following recursive definition:

f(x) =x+3 if x <=0



f(x)=f(x-3)+(x+5) otherwise

My attempt:

#include <stdio.h>

int f(int x); //Prototype to call to f



int main(void) {

  int n; //number the user will input



//Ask user to input data an reads it

  printf("Enter a whole number: ");

  scanf("%d", &n);



//Pointer for f

  f(n);



//Prints results

  printf("nn is %dn", n);

  printf("f(x) is %dn", f(n));

  return 0;

}



int f(int x) {

//Checks if equal to zero

  if (x <= 0) {

     x + 3;

  }

//If not equal to zero then do this

  else {

     f(x - 3) + (x + 5);

  }

}

Thank you all for the help, learned a lot from your comments and suggestions.
I was able to get it work I believe https://pastebin.com/v9cZHvy0

edited Nov 28 '18 at 4:51

asked Nov 28 '18 at 4:03

Alec Mauro

Every recursive function has (1) an exit condition, and (2) a recursive call. You provide no exit condition. Further, you need scanf("%d", &n) (note the '&') and you must validate the return, e.g. if (scanf("%d", &n) != 1) { /* handle error */ }. Your call to f(n); is not a // Pointer for f it is simply a function call (that makes little sense there). Think through how your set of recursive calls must exit. As it is the computation of (x-3)+(x+5) grows in size so x <= 0 cannot be the exit condition.

– David C. Rankin
Nov 28 '18 at 4:33

@DavidC.Rankin: The exit condition is x <= 0. It seems you may have missed the fact that f(x-3) calls f and (x+5) does not.

– Eric Postpischil
Nov 28 '18 at 4:36

Yes, I read it as f (x-3 + x + 5).

– David C. Rankin
Nov 28 '18 at 4:37

add a comment |

Write a program that queries the user for an integer value and uses a recursive

function that returns the value of the following recursive definition:

f(x) =x+3 if x <=0



f(x)=f(x-3)+(x+5) otherwise

My attempt:

#include <stdio.h>

int f(int x); //Prototype to call to f



int main(void) {

  int n; //number the user will input



//Ask user to input data an reads it

  printf("Enter a whole number: ");

  scanf("%d", &n);



//Pointer for f

  f(n);



//Prints results

  printf("nn is %dn", n);

  printf("f(x) is %dn", f(n));

  return 0;

}



int f(int x) {

//Checks if equal to zero

  if (x <= 0) {

     x + 3;

  }

//If not equal to zero then do this

  else {

     f(x - 3) + (x + 5);

  }

}

Thank you all for the help, learned a lot from your comments and suggestions.
I was able to get it work I believe https://pastebin.com/v9cZHvy0

edited Nov 28 '18 at 4:51

asked Nov 28 '18 at 4:03

Alec Mauro

Write a program that queries the user for an integer value and uses a recursive

function that returns the value of the following recursive definition:

f(x) =x+3 if x <=0



f(x)=f(x-3)+(x+5) otherwise

My attempt:

#include <stdio.h>

int f(int x); //Prototype to call to f



int main(void) {

  int n; //number the user will input



//Ask user to input data an reads it

  printf("Enter a whole number: ");

  scanf("%d", &n);



//Pointer for f

  f(n);



//Prints results

  printf("nn is %dn", n);

  printf("f(x) is %dn", f(n));

  return 0;

}



int f(int x) {

//Checks if equal to zero

  if (x <= 0) {

     x + 3;

  }

//If not equal to zero then do this

  else {

     f(x - 3) + (x + 5);

  }

}

Thank you all for the help, learned a lot from your comments and suggestions.
I was able to get it work I believe https://pastebin.com/v9cZHvy0

c recursion

edited Nov 28 '18 at 4:51

asked Nov 28 '18 at 4:03

Alec Mauro

edited Nov 28 '18 at 4:51

asked Nov 28 '18 at 4:03

Alec Mauro

edited Nov 28 '18 at 4:51

asked Nov 28 '18 at 4:03

Alec Mauro

asked Nov 28 '18 at 4:03

Alec Mauro

asked Nov 28 '18 at 4:03

Alec Mauro

Every recursive function has (1) an exit condition, and (2) a recursive call. You provide no exit condition. Further, you need scanf("%d", &n) (note the '&') and you must validate the return, e.g. if (scanf("%d", &n) != 1) { /* handle error */ }. Your call to f(n); is not a // Pointer for f it is simply a function call (that makes little sense there). Think through how your set of recursive calls must exit. As it is the computation of (x-3)+(x+5) grows in size so x <= 0 cannot be the exit condition.

– David C. Rankin
Nov 28 '18 at 4:33

@DavidC.Rankin: The exit condition is x <= 0. It seems you may have missed the fact that f(x-3) calls f and (x+5) does not.

– Eric Postpischil
Nov 28 '18 at 4:36

Yes, I read it as f (x-3 + x + 5).

– David C. Rankin
Nov 28 '18 at 4:37

add a comment |

Every recursive function has (1) an exit condition, and (2) a recursive call. You provide no exit condition. Further, you need scanf("%d", &n) (note the '&') and you must validate the return, e.g. if (scanf("%d", &n) != 1) { /* handle error */ }. Your call to f(n); is not a // Pointer for f it is simply a function call (that makes little sense there). Think through how your set of recursive calls must exit. As it is the computation of (x-3)+(x+5) grows in size so x <= 0 cannot be the exit condition.

– David C. Rankin
Nov 28 '18 at 4:33

@DavidC.Rankin: The exit condition is x <= 0. It seems you may have missed the fact that f(x-3) calls f and (x+5) does not.

– Eric Postpischil
Nov 28 '18 at 4:36

Yes, I read it as f (x-3 + x + 5).

– David C. Rankin
Nov 28 '18 at 4:37

Every recursive function has (1) an exit condition, and (2) a recursive call. You provide no exit condition. Further, you need scanf("%d", &n) (note the '&') and you must validate the return, e.g. if (scanf("%d", &n) != 1) { /* handle error */ }. Your call to f(n); is not a // Pointer for f it is simply a function call (that makes little sense there). Think through how your set of recursive calls must exit. As it is the computation of (x-3)+(x+5) grows in size so x <= 0 cannot be the exit condition.

– David C. Rankin
Nov 28 '18 at 4:33

@DavidC.Rankin: The exit condition is x <= 0. It seems you may have missed the fact that f(x-3) calls f and (x+5) does not.

– Eric Postpischil
Nov 28 '18 at 4:36

Yes, I read it as f (x-3 + x + 5).

– David C. Rankin
Nov 28 '18 at 4:37

add a comment |

2 Answers
2

active

oldest

votes

as far as I can see first one is scanf

scanf("%d", &n);

second one is your function f is not returning anything, so this

int f(int x) {

//Checks if equal to zero

  if (x <= 0)

  {

     return (x + 3);

  }



  return ( f(x-3) + (x+5) );

}

minor - the below statement is actually useless

//Pointer for f

  f(n);

answered Nov 28 '18 at 4:34

u__

2,5771029

The additional return ( ... ) parenthesis are superfluous, but good call on the function setup.

– David C. Rankin
Nov 28 '18 at 4:36

add a comment |

As a student of life, I am always willing to help a fellow academic:

Your code has a few errors that should be of note:

int f(int x) has no return statement, even though it is expecting an integer. I assume you wish to return the result of the program (See Issue #3).

You execute f(n) twice. First on line 12, then again on line 16. printf("f(x) is %dn", f(n)); actually executes F(n) in order to receive its return value to associate with the %d format specifier.

You have not assigned x+3 OR f(x-3) + (x+5) to any integer. These statements do not save the return values of f(x) that you need to return.

This link may be of help to you:

https://www.geeksforgeeks.org/c-function-argument-return-values/

Notice specifically how the output of functions are captured.

Hope this helps (And I wish you academic success!)

answered Nov 28 '18 at 4:25

armitus

3159

Also, the scanf statement misses a &

– Canh
Nov 28 '18 at 4:28

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

as far as I can see first one is scanf

scanf("%d", &n);

second one is your function f is not returning anything, so this

int f(int x) {

//Checks if equal to zero

  if (x <= 0)

  {

     return (x + 3);

  }



  return ( f(x-3) + (x+5) );

}

minor - the below statement is actually useless

//Pointer for f

  f(n);

answered Nov 28 '18 at 4:34

u__

2,5771029

The additional return ( ... ) parenthesis are superfluous, but good call on the function setup.

– David C. Rankin
Nov 28 '18 at 4:36

add a comment |

as far as I can see first one is scanf

scanf("%d", &n);

second one is your function f is not returning anything, so this

int f(int x) {

//Checks if equal to zero

  if (x <= 0)

  {

     return (x + 3);

  }



  return ( f(x-3) + (x+5) );

}

minor - the below statement is actually useless

//Pointer for f

  f(n);

answered Nov 28 '18 at 4:34

u__

2,5771029

The additional return ( ... ) parenthesis are superfluous, but good call on the function setup.

– David C. Rankin
Nov 28 '18 at 4:36

add a comment |

as far as I can see first one is scanf

scanf("%d", &n);

second one is your function f is not returning anything, so this

int f(int x) {

//Checks if equal to zero

  if (x <= 0)

  {

     return (x + 3);

  }



  return ( f(x-3) + (x+5) );

}

minor - the below statement is actually useless

//Pointer for f

  f(n);

answered Nov 28 '18 at 4:34

u__

2,5771029

as far as I can see first one is scanf

scanf("%d", &n);

second one is your function f is not returning anything, so this

int f(int x) {

//Checks if equal to zero

  if (x <= 0)

  {

     return (x + 3);

  }



  return ( f(x-3) + (x+5) );

}

minor - the below statement is actually useless

//Pointer for f

  f(n);

answered Nov 28 '18 at 4:34

u__

2,5771029

answered Nov 28 '18 at 4:34

u__

2,5771029

answered Nov 28 '18 at 4:34

u__

2,5771029

answered Nov 28 '18 at 4:34

u__

2,5771029

The additional return ( ... ) parenthesis are superfluous, but good call on the function setup.

– David C. Rankin
Nov 28 '18 at 4:36

add a comment |

The additional return ( ... ) parenthesis are superfluous, but good call on the function setup.

– David C. Rankin
Nov 28 '18 at 4:36

The additional return ( ... ) parenthesis are superfluous, but good call on the function setup.

– David C. Rankin
Nov 28 '18 at 4:36

add a comment |

As a student of life, I am always willing to help a fellow academic:

Your code has a few errors that should be of note:

int f(int x) has no return statement, even though it is expecting an integer. I assume you wish to return the result of the program (See Issue #3).

You execute f(n) twice. First on line 12, then again on line 16. printf("f(x) is %dn", f(n)); actually executes F(n) in order to receive its return value to associate with the %d format specifier.

You have not assigned x+3 OR f(x-3) + (x+5) to any integer. These statements do not save the return values of f(x) that you need to return.

This link may be of help to you:

https://www.geeksforgeeks.org/c-function-argument-return-values/

Notice specifically how the output of functions are captured.

Hope this helps (And I wish you academic success!)

answered Nov 28 '18 at 4:25

armitus

3159

Also, the scanf statement misses a &

– Canh
Nov 28 '18 at 4:28

add a comment |

As a student of life, I am always willing to help a fellow academic:

Your code has a few errors that should be of note:

int f(int x) has no return statement, even though it is expecting an integer. I assume you wish to return the result of the program (See Issue #3).

You execute f(n) twice. First on line 12, then again on line 16. printf("f(x) is %dn", f(n)); actually executes F(n) in order to receive its return value to associate with the %d format specifier.

You have not assigned x+3 OR f(x-3) + (x+5) to any integer. These statements do not save the return values of f(x) that you need to return.

This link may be of help to you:

https://www.geeksforgeeks.org/c-function-argument-return-values/

Notice specifically how the output of functions are captured.

Hope this helps (And I wish you academic success!)

answered Nov 28 '18 at 4:25

armitus

3159

Also, the scanf statement misses a &

– Canh
Nov 28 '18 at 4:28

add a comment |

As a student of life, I am always willing to help a fellow academic:

Your code has a few errors that should be of note:

int f(int x) has no return statement, even though it is expecting an integer. I assume you wish to return the result of the program (See Issue #3).

You execute f(n) twice. First on line 12, then again on line 16. printf("f(x) is %dn", f(n)); actually executes F(n) in order to receive its return value to associate with the %d format specifier.

You have not assigned x+3 OR f(x-3) + (x+5) to any integer. These statements do not save the return values of f(x) that you need to return.

This link may be of help to you:

https://www.geeksforgeeks.org/c-function-argument-return-values/

Notice specifically how the output of functions are captured.

Hope this helps (And I wish you academic success!)

answered Nov 28 '18 at 4:25

armitus

3159

As a student of life, I am always willing to help a fellow academic:

Your code has a few errors that should be of note:

int f(int x) has no return statement, even though it is expecting an integer. I assume you wish to return the result of the program (See Issue #3).

You execute f(n) twice. First on line 12, then again on line 16. printf("f(x) is %dn", f(n)); actually executes F(n) in order to receive its return value to associate with the %d format specifier.

You have not assigned x+3 OR f(x-3) + (x+5) to any integer. These statements do not save the return values of f(x) that you need to return.

This link may be of help to you:

https://www.geeksforgeeks.org/c-function-argument-return-values/

Notice specifically how the output of functions are captured.

Hope this helps (And I wish you academic success!)

answered Nov 28 '18 at 4:25

armitus

3159

answered Nov 28 '18 at 4:25

armitus

3159

answered Nov 28 '18 at 4:25

armitus

3159

answered Nov 28 '18 at 4:25

armitus

3159

Also, the scanf statement misses a &

– Canh
Nov 28 '18 at 4:28

add a comment |

Also, the scanf statement misses a &

– Canh
Nov 28 '18 at 4:28

Also, the scanf statement misses a &

– Canh
Nov 28 '18 at 4:28

add a comment |

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