What is the difference between x.pow(n) and pow(x, n)?

Question

I'm wondering because when I run my code in checked mode there seems to be some discrepancies. For example: ``` List getFactors(int n) { List factors = [[1, n]]; double top = pow(n,1/2); int test = 2; while (test <= top) { if (n % test == 0) factors.add([test, n ~/ test]); test++; } return factors; } ``` works as is, but when I change the `pow(n,1/2)` to `n.pow(1/2)` it returns an error in checked mode. The only fix is to change the type of `n` to a double. Why is this? Also the general differences between the two would be nice to know. Thanks!

Accepted Answer

Update: int/num/double.pow() currently exist only in the VM, and will be removed. Use math.pow() instead.

The signature for int.pow() is:

```
int pow(int exponent)
```

So the following example fails in checked mode as 1/2 does not evaluate to an integer.

```
int i = 5;
i.pow(1/2);
```

So calling int.pow() expects an integer exponent (Only checked in checked mode), and returns an integer.

And, calling math.pow(num x, num exponent), does not require an integer exponent, and may return a double, if x is an integer and exponent is a double.

Here is a link to the math.pow() documentation. Here are links to the int.pow() and math.pow() source code so you can see what happens under the hood.

What is the difference between x.pow(n) and pow(x, n)?

Solution

Problem