Hello everyone
i 'm a newbie in c and i have this exercise :
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What the error in the following function ?
--------------------------------------------------------------------------------Code:void f(void) { int i ; printf("n f() \n"); /* calling f function 5 times */ for (i=0;i<=5;i++) f() ; }
I can see no mistake . Can you ? It's kinf of urgent and any help would be deeeeeply appreciated
Thanks a lot
I agree there's no syntax error in the function. Logic errors, now, that's something else.
tab thanks for replying.
In order to see logical errors , there should be something asked like "this function is supposed to do "this" ..." , but there isn't .
It is in the comment: "calling f function 5 times". Presumably you get bonus marks if you take it a step further.Originally Posted by johngav
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EDIT: put my foot in my mouth there lol
Hint: what is the value of i when the function enters the loop on the second time it is called.
Last edited by KBriggs; 06-24-2009 at 11:03 AM.
KBriggs , no , it is an idefinat loop , i run it with dev++ and it prints n f() many many times till the execution window closes
laser , i agree that the comment is the key , but what would be a step further?
What is the name of the function that is being defined? What is the name of the function that is being called?
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laser , f is the name in both cases , so it is a reccuring function , so ? Ican't get any further
kbriggs the value is 1 isn't it ? , but that's not very helpful
The error is in the increment step. Consider:
When is i incremented in that function? Before or after f() is called again? Which one should it be?Code:void f(void) { int i ; printf("n f() \n"); /* calling f function 5 times */ for (i=0;i<=5;i++) f() ; }
Also, you are resetting i each time the function is called. I don't think that i can be local to a recursive function if you want it to hold increments between recursive calls.
Code:int i = 0; void f(void) { printf("n f() \n"); /* calling f function 5 times */ while (i <= 5) { i++; f(); } } int main() { f(); }
Last edited by KBriggs; 06-24-2009 at 11:12 AM.
So what is the base case for the recursion?
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kbriggs i guess it is incremented after f calling and that's probably the reason it is indefinate. but how should it be?
laserlight , do you mean why is recursion used in this case? I don;t know
Try printing the value of i each time you call your function. You will see that it never gets incremented in your code because the next call to f() happens before the increment step, and it will repeat until the system segfaults.
No. I mean that there is no scenario in which the recursion will terminate, hence there is infinite recursion.
As for the obvious problem that you appear to be missing. Let us assume that there is a function named g that takes no arguments, and that f and g are not mutually recursive. What is wrong with the implementation of this function f?
Code:void f(void) { int i ; printf("n f() \n"); /* calling g function 5 times */ for (i=0;i<=5;i++) g() ; }
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I see your point Kbriggs .seems like a stupid exercise though no ? I mean how would this function not be wrong ? What would you change
