Negative Power of a Number in Clarity

[c0d3rk1d]

Describe the bug
Inconsistent power function behavior.

Steps To Reproduce
Open the clarinet console and type

(pow 0 -2)
and
(pow 5 -1)

Expected behavior
(pow 0 -2) should return error since it is infinity number and (pow 5 -1) should return zero...

Environment (please complete the following information):

• OS: MacOs
• Clarinet Console 0.33

Additional context

[c0d3rk1d]

p.s. I submitted the same issue to Clarinet Console repo.

[c0d3rk1d]

Similar to (pow 0 -2)

(log2 0) is an infinity number, and throws an error...

[c0d3rk1d]

Here are the test cases... Excell Power function vs Clarity Pow function

[obycode]

Echoing my Discord comments here for record:

The code handling pow looks like this, which explains those cases:

                if base == 0 && power == 0 {
                    // Note that 0⁰ (pow(0, 0)) returns 1. Mathematically this is undefined (https://docs.rs/num-traits/0.2.10/num_traits/pow/fn.pow.html)
                    return Self::make_value(1);
                }
                if base == 1 {
                    return Self::make_value(1);
                }

                if base == 0 {
                    return Self::make_value(0);
                }

                if power == 1 {
                    return Self::make_value(base);
                }

                if power < 0 || power > (u32::MAX as $type) {
                    return Err(RuntimeErrorType::Arithmetic(
                        "Power argument to (pow ...) must be a u32 integer".to_string(),
                    )
                    .into());
                }

I think the behavior is reasonable, even though it is different, so the cleanest solution for now will be to update the documentation to make this behavior clear.

[c0d3rk1d]

More test data; I have done these tests yesterday, just forgot to post it here.

Base	Power	Clarity	Javascript	Result
-5	-5	error	0	X
-5	-3	error	0	X
-5	-1	error	0	X
-5	0	1	1
-5	1	-5	-5
-5	3	-125	-125
-5	5	-3125	-3125
-3	-5	error	0	X
-3	-3	error	0	X
-3	-1	error	0	X
-3	0	1	1
-3	1	-3	-3
-3	3	-27	-27
-3	5	-243	-243
-1	-5	error	-1	X
-1	-3	error	-1	X
-1	-1	error	-1	X
-1	0	1	1
-1	1	-1	-1
-1	3	-1	-1
-1	5	-1	-1
0	-5	0	Infinity	X
0	-3	0	Infinity	X
0	-1	0	Infinity	X
0	0	1	1
0	1	0	0
0	3	0	0
0	5	0	0
1	-5	1	1
1	-3	1	1
1	-1	1	1
1	0	1	1
1	1	1	1
1	3	1	1
1	5	1	1
3	-5	error	0	X
3	-3	error	0	X
3	-1	error	0	X
3	0	1	1
3	1	3	3
3	3	27	27
3	5	243	243
5	-5	error	0	X
5	-3	error	0	X
5	-1	error	0	X
5	0	1	1
5	1	5	5
5	3	125	125
5	5	3125	3125

[jcnelson]

The consensus at the blockchain meeting is that pow exhibits well-defined behavior as-is. The issue is that it was not properly documented. @obycode will address the documentation.

[jcnelson]

Docs have been merged, so closing this.

[blockstack-devops]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.