any negative power is an error

[thedavidmeister]

Motivation

Solution

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Summary by CodeRabbit

• Tests
  • Added a new test to verify that raising a negative base to a non-zero power results in an expected error.

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Walkthrough

A new test, testNegativePowError, was added to the LibDecimalFloatPowTest contract to verify that the pow function in LibDecimalFloat reverts with a Log10Negative error when the base is negative and the exponent is non-zero. Imports were updated to support this test. No other code or tests were changed.

Changes

Cohort / File(s)	Change Summary
Negative Base Exponentiation Test test/src/lib/LibDecimalFloat.pow.t.sol	Added testNegativePowError to check that pow reverts with Log10Negative for negative base and nonzero exponent. Updated imports for error and normalization utility.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~6 minutes

Possibly related PRs

• pow 0 #87: The main PR adds a test for negative base exponentiation reverting with Log10Negative, while the retrieved PR modifies the pow function to handle zero base and zero exponent cases and adds related tests; since they address different edge cases and errors in the pow function, the changes are related but focus on distinct input scenarios.

Note

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📥 Commits

Reviewing files that changed from the base of the PR and between ec7efec and 8d0befe.

📒 Files selected for processing (1)

• test/src/lib/LibDecimalFloat.pow.t.sol (2 hunks)

🧰 Additional context used

🧠 Learnings (2)

📓 Common learnings

Learnt from: 0xgleb
PR: rainlanguage/rain.math.float#59
File: crates/float/src/lib.rs:233-242
Timestamp: 2025-06-17T10:17:56.205Z
Learning: In the rainlanguage/rain.math.float repository, the maintainer 0xgleb prefers to handle documentation additions and improvements in separate issues rather than inline with feature PRs.

Learnt from: rouzwelt
PR: rainlanguage/rain.math.float#76
File: test_js/float.test.ts:9-32
Timestamp: 2025-07-17T02:38:44.698Z
Learning: In the rainlanguage/rain.math.float repository, the user rouzwelt accepts non-null assertions in test files because tests should throw and fail immediately when something goes wrong, making it clear where the issue occurred.

Learnt from: 0xgleb
PR: rainlanguage/rain.math.float#70
File: crates/float/src/evm.rs:38-43
Timestamp: 2025-07-03T11:20:50.456Z
Learning: In the rainlanguage/rain.math.float codebase, the user 0xgleb prefers not to add explanatory comments for well-established Rust idioms like the double `?` pattern, as these are self-explanatory to experienced Rust developers and don't need over-commenting.

Learnt from: 0xgleb
PR: rainlanguage/rain.math.float#58
File: src/concrete/DecimalFloat.sol:175-182
Timestamp: 2025-06-16T13:17:28.513Z
Learning: In the rainlanguage/rain.math.float codebase, there's an established naming convention where functions accepting a `Float` type parameter consistently use `float` as the parameter name, even though it shadows the type name. This pattern is used throughout `LibDecimalFloat.sol` and should be maintained for consistency in related contracts like `DecimalFloat.sol`.

test/src/lib/LibDecimalFloat.pow.t.sol (6)

Learnt from: 0xgleb
PR: #58
File: src/concrete/DecimalFloat.sol:175-182
Timestamp: 2025-06-16T13:17:28.513Z
Learning: In the rainlanguage/rain.math.float codebase, there's an established naming convention where functions accepting a Float type parameter consistently use float as the parameter name, even though it shadows the type name. This pattern is used throughout LibDecimalFloat.sol and should be maintained for consistency in related contracts like DecimalFloat.sol.

Learnt from: rouzwelt
PR: #83
File: src/concrete/DecimalFloat.sol:248-251
Timestamp: 2025-07-24T04:32:14.171Z
Learning: In the rainlanguage/rain.math.float project, functions in DecimalFloat.sol that return tuples from LibDecimalFloat calls must unpack the tuple into local variables before returning them (rather than returning directly) to maintain compatibility with Slither static analysis checks.

Learnt from: 0xgleb
PR: #58
File: crates/float/src/lib.rs:382-401
Timestamp: 2025-06-16T13:19:32.009Z
Learning: In the rainlanguage/rain.math.float codebase, variable shadowing in property tests like test_lt_eq_gt_with_add is acceptable when it represents a logical progression of the same conceptual value being tested through different states.

Learnt from: thedavidmeister
PR: #30
File: test/src/lib/LibDecimalFloat.gt.t.sol:33-36
Timestamp: 2025-04-25T03:58:01.307Z
Learning: In the rain.math.float library, all values of Float (which is a type alias for bytes32) are considered valid and can be safely used with methods like gt(), lt(), or eq() without causing reverts.

Learnt from: rouzwelt
PR: #76
File: test_js/float.test.ts:9-32
Timestamp: 2025-07-17T02:38:44.698Z
Learning: In the rainlanguage/rain.math.float repository, the user rouzwelt accepts non-null assertions in test files because tests should throw and fail immediately when something goes wrong, making it clear where the issue occurred.

Learnt from: 0xgleb
PR: #46
File: crates/float/proptest-regressions/lib.txt:1-3
Timestamp: 2025-06-11T09:03:20.771Z
Learning: The file crates/float/proptest-regressions/lib.txt is automatically generated by proptest and should not be manually edited.

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🔇 Additional comments (2)

test/src/lib/LibDecimalFloat.pow.t.sol (2)

7-8: LGTM! Imports added for new test functionality.

The added imports support the new test:

• Log10Negative error for the expected revert condition
• LibDecimalFloatImplementation for normalization functionality used in the test

---

48-66: Negative-base error test is correct and aligns with implementation

• In src/lib/LibDecimalFloat.sol, pow computes 10^(b * log10(a)), invoking LibDecimalFloatImplementation.log10, which immediately reverts Log10Negative(signedCoefficient, exponent) when the (normalized) coefficient is negative.
• The test’s call to LibDecimalFloatImplementation.normalize(...) exactly mirrors how log10 receives its inputs, so the revert selector and arguments match precisely.
• The assumptions !a.isZero() and !b.isZero() correctly exclude the well-defined zero-base and zero-exponent cases.

No changes required.

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