Turing VS C++ (Recursive Counting)

[Flikerator]

Don't really know what to do to learn some more C++, having trouble finding anything about Voids (Except programs that already have them, in which case they don't explain what they are, or how they work). I guess I could mess around and figure them out, but I like tutorials (More then one, and then experimenting, so I don't get the wrong idea).

Since I was bored, I made an extremely simple recursive factoring program. Im terrible at recursive programs (I can formulate them in my head, but writing the code I have no were to start.), practice breeds improvement right?

code:

#include <iostream> double Factor (double x); int main() {  for (int i=1; i<171; i++)  {      std::cout << i << " " << Factor (i) << std::endl;  }   std::cin.ignore();  return 0; } double Factor (double x) {       if (x==1)       {          return 1;       }       return x * Factor (x-1); }

If you have any alternative ways to do this recursivly, let me know =P

[wtd]

code:

double Factor (double x) {       if (x==1)       {          return 1;       }       return x * Factor (x-1); }

Let me suggest something here, first.

What you have is exactly identical to having an "else" clause. So just use the else clause.

code:

double Factor(double x) {       if (x == 1)       {          return 1;       }       else       {             return x * Factor(x - 1);       } }

For something this simple, we might also rewrite this as:

code:

double Factor(double x) {       return x == 1 ? 1 : x * Factor(x - 1); }

Secondly, there's a problem with using floating point numbers in this case. Let's say we write:

code:

Factor(1.5)

Now, since this isn't 1, we next execute:

code:

1.5 * Factor(0.5)

And 0.5 isn't 1, so next...

code:

1.5 * 0.5 * Factor(-0.5)

Will this ever terminate?

[Flikerator]

At first I thought about putting an else, but realised it wasn't needed, because its just extra code for no reason. Unless im missing something.

That is really neat. As I understand it;

does x == 1? then return 1

Then the ":" would be like an else right? Thats really neat.

As for that error, it was meant only to be ints. Why I put Double I have no idea. Ive never heard of Factoring real numbers My Turing version has ints so I guess I goofed =P

Thanks wtd for all the help ^_^

[Null]

Just a note. This is not rule by any means, but functions in C++ typically begin with a lowercase letter.

[wtd]

Additionally, what is being done is not "factoring", but generating a factorial. The function name should indicate this.

A recursive factorial function with O(1) space properties:

code:

let factorial n =   let rec aux n acc =     if n = 0 then acc     else aux (n - 1) (n * acc)   in     aux n 1

Or perhaps:

code:

(defgeneric factorial (n)) (defmethod factorial ((n integer))   (labels ((aux (n acc)              (if (equalp n 0)                  acc                  (aux (- n 1) (* n acc)))))     (aux n 1)))

[Andy]

Null wrote:

Just a note. This is not rule by any means, but functions in C++ typically begin with a lowercase letter.

Just a note. This is not a rule by any means, but people generally read a few pages ahead before posting