Missing Conditional

Hi. I have the following code which runs perfectly for every case except a negative number. This program outputs 1 if the argument in perfectSquare() is an fact a perfect square (and 0 otherwise). Can someone give me a conditional statement which will get the negative number scenario going? Thanks. Steve

Code:

---

#include<iostream>

using namespace std;

bool perfectSquare(int);

int main()
{
        cout<<perfectSquare(0)<<endl;
        return 0;
}

bool perfectSquare(int x)
{
      int y;
      for(y=0;y<=x;y++)
      {
          if(x==(y*y))
          return true;
      }
      return false;
}

---

Square roots of negative numbers are unreal. Unless you want to make it positive and then append an "i" to everything, you could just add a conditional for a negative number at the beginning, and if it returns true, end the function with an error message or something.

Code:

---

#include <cmath>
 
bool perfectSquare(int x)
{
  if(x < 0)
        return false; //assuming negatives cannot be perfect squares
 
  double root = sqrt(x);
  int truncated = root;
 
  return ((double)truncated == root);
}

---

Note that your original function was returning 1 and 0, while the return type of the function is bool.

Or if you want to automatically change negative numbers to positive and continue...

Code:

---

  if(x < 0) x = x * -1;

---

-d-

>>if(x < 0) x = x * -1;

Code:

---

#include <cmath>
x = abs(x);
-or-
x = (x >=0) ? x:-x;
-or-
if(x < 0) x = -x;

---

Do squares of unreal numbers really count as perfect squares though?

>>if(x < 0) x = x * -1;
>#include <cmath>
>x = abs(x);

I vote for one fewer include.

>Do squares of unreal numbers really count as perfect squares?

A program can react in different ways when it encounters "bad" input

"You entered a negative number (-234) did you mean 234?"

-d-

> if(x < 0) x = -x;

Ok, you win.

>>I vote for one fewer include.
There are two other alternatives I posted. At least they don't involve direct multiplication ;)

>>A program can react in different ways when it encounters "bad" input
A negative number is not bad input, unless the coder so designates it - and if it is 'bad' ("please enter a positive number"), then the coder should filter the input before passing it to a function. The point was, if a negative number CANNOT be a perfect square, then obviously perfectSquare() should return false when a negative is encountered. Your example would simply ignore the fact that it is not a perfect square (again, assuming that negatives are by definition not perfect squares - hence my question) and potentially give incorrect output.

Quote:

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Originally Posted by Hunter2

>>I vote for one fewer include.
There are two other alternatives I posted. At least they don't involve direct multiplication ;)

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Sorry, I replied before your edit adding the 2nd and 3rd alternatives.

Quote:

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Originally Posted by Hunter2

A negative number is not bad input, unless the coder so designates it

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Hence my quotes around the word bad.

Quote:

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Originally Posted by Hunter2

...if a negative number CANNOT be a perfect square, then obviously perfectSquare() should return false when a negative is encountered. Your example would simply ignore the fact that it is not a perfect square (again, assuming that negatives are by definition not perfect squares - hence my question) and potentially give incorrect output.

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I cannot argue here.

Truce :(

-d-

Truce :) Heh, and we have yet to hear from the OP...