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WalkthroughThe UD30x9 fixed-point math implementation now includes bounds checks in Changes
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
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🧹 Nitpick comments (2)
math/fixed_point/sources/ud30x9/ud30x9_base.move (1)
86-87: Document the newbits >= 128 => 0behavior in function docs.The implementation changed semantics at the boundary; the doc comments should state this explicitly to avoid API ambiguity.
Proposed doc update
-/// Implements the left shift operation (<<) for `UD30x9` type. +/// Implements the left shift operation (<<) for `UD30x9` type. +/// Returns zero when `bits >= 128`. public fun lshift(x: UD30x9, bits: u8): UD30x9 { @@ -/// Implements the right shift operation (>>) for `UD30x9` type. +/// Implements the right shift operation (>>) for `UD30x9` type. +/// Returns zero when `bits >= 128`. public fun rshift(x: UD30x9, bits: u8): UD30x9 {Also applies to: 158-159
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@math/fixed_point/sources/ud30x9/ud30x9_base.move` around lines 86 - 87, The function docs for lshift (and the analogous right-shift function at the same region) must explicitly state the new boundary behavior: when the shift amount bits is >= 128 the result is defined to be 0; update the doc comment above public fun lshift(x: UD30x9, bits: u8): UD30x9 to mention "bits >= 128 => 0" and add the same clarifying sentence to the doc comment for the corresponding rshift function (the other shift function at lines ~158-159) so callers are aware of the changed semantics and the exact behavior at the boundary.math/fixed_point/tests/ud30x9_tests.move (1)
122-144: Addbits = 127boundary tests to guard off-by-one regressions.You now assert saturation at and above 128; adding explicit 127 checks would lock down the threshold behavior.
Suggested test additions
+#[test] +fun lshift_by_127_keeps_shift_semantics() { + let x = fixed(1); + expect(x.lshift(127), fixed(1u128 << 127)); +} + +#[test] +fun rshift_by_127_keeps_shift_semantics() { + let x = fixed(MAX_VALUE); + expect(x.rshift(127), fixed(1)); +}🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@math/fixed_point/tests/ud30x9_tests.move` around lines 122 - 144, Add two boundary tests for the 127-bit case to prevent off-by-one regressions: in math/fixed_point/tests/ud30x9_tests.move add a lshift_by_127_not_zero test and a rshift_by_127_not_zero test that use let x = fixed(1) and call x.lshift(127) and x.rshift(127) respectively, asserting the results are not equal to fixed(0) (i.e., expect non-zero) so the threshold at 128 is explicitly verified; place them alongside the existing lshift_by_128_returns_zero and rshift_by_128_returns_zero tests.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Nitpick comments:
In `@math/fixed_point/sources/ud30x9/ud30x9_base.move`:
- Around line 86-87: The function docs for lshift (and the analogous right-shift
function at the same region) must explicitly state the new boundary behavior:
when the shift amount bits is >= 128 the result is defined to be 0; update the
doc comment above public fun lshift(x: UD30x9, bits: u8): UD30x9 to mention
"bits >= 128 => 0" and add the same clarifying sentence to the doc comment for
the corresponding rshift function (the other shift function at lines ~158-159)
so callers are aware of the changed semantics and the exact behavior at the
boundary.
In `@math/fixed_point/tests/ud30x9_tests.move`:
- Around line 122-144: Add two boundary tests for the 127-bit case to prevent
off-by-one regressions: in math/fixed_point/tests/ud30x9_tests.move add a
lshift_by_127_not_zero test and a rshift_by_127_not_zero test that use let x =
fixed(1) and call x.lshift(127) and x.rshift(127) respectively, asserting the
results are not equal to fixed(0) (i.e., expect non-zero) so the threshold at
128 is explicitly verified; place them alongside the existing
lshift_by_128_returns_zero and rshift_by_128_returns_zero tests.
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immrsd
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Mar 3, 2026
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LGTM! Slightly improved the doc to be more informative and consistent with SD29x9 docs
bidzyyys
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165-bug-inconsistent-shift-behavior-in-fixed-point-math-library
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This was referenced Mar 3, 2026
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Resolves #165
Summary by CodeRabbit
Bug Fixes
Tests