99 lines
No EOL
3 KiB
Markdown
99 lines
No EOL
3 KiB
Markdown
# Likewise - Floating Point Diff Implementation
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## Codebase Structure
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```
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src/
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├── lib.rs # Main entry, re-exports
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├── types.rs # DiffOp, Change, ChangeTag, Algorithm enums
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├── common.rs # capture_diff_slices(), get_diff_ratio()
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├── algorithms/ # myers.rs, patience.rs, lcs.rs, hook.rs, utils.rs
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├── text/ # TextDiff, DiffableStr trait
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├── udiff.rs # Unified diff output
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└── utils.rs # Text utilities
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```
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## Current Diff Flow
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1. `capture_diff_slices(alg, &old, &new)` → `Vec<DiffOp>`
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2. `DiffOp::iter_changes(&old, &new)` → `Iterator<Change<T>>`
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3. Requires `T: Hash + Eq + Ord`
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## Key Types
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```rust
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pub enum DiffOp {
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Equal { old_index: usize, new_index: usize, len: usize },
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Delete { old_index: usize, old_len: usize, new_index: usize },
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Insert { old_index: usize, new_index: usize, new_len: usize },
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Replace { old_index: usize, old_len: usize, new_index: usize, new_len: usize },
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}
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pub struct Change<T> {
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pub(crate) tag: ChangeTag,
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pub(crate) old_index: Option<usize>,
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pub(crate) new_index: Option<usize>,
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pub(crate) value: T,
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}
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```
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## Algorithm Trait
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```rust
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pub trait DiffHook {
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type Error;
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fn equal(&mut self, old: usize, new: usize, len: usize) -> Result<(), Self::Error>;
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fn delete(&mut self, old: usize, old_len: usize, new: usize) -> Result<(), Self::Error>;
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fn insert(&mut self, old: usize, new: usize, new_len: usize) -> Result<(), Self::Error>;
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fn replace(&mut self, old: usize, old_len: usize, new: usize, new_len: usize) -> Result<(), Self::Error>;
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}
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```
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## Task: FP Comparison
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Add eps/ulps floating point comparison for f32/f64 slices.
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### Implementation Points
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1. **New comparison trait** alongside existing `PartialEq` requirement
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2. **Algorithm modification** to use FP-aware comparison in core loops
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3. **API surface** for specifying epsilon/ulps parameters
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4. **Testing** edge cases: NaN, infinity, subnormals, precision boundaries
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### Files to Modify
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- `src/algorithms/myers.rs` - Core comparison logic
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- `src/algorithms/patience.rs` - Core comparison logic
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- `src/algorithms/lcs.rs` - Core comparison logic
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- `src/common.rs` - Add FP-aware `capture_diff_slices_fp()`
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- `examples/floating_point.rs` - Usage demonstration
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### Example Usage Goal
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```rust
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let old = vec![1.0, 2.0, 3.0];
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let new = vec![1.000001, 2.0, 3.1];
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// Absolute epsilon
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let ops = capture_diff_slices_fp_eps(Algorithm::Myers, &old, &new, 0.0001);
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// Relative ulps
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let ops = capture_diff_slices_fp_ulps(Algorithm::Myers, &old, &new, 4);
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```
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### Testing Strategy
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Use existing `insta` snapshot testing framework. Test matrices:
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- Normal values with various epsilon/ulps settings
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- Edge cases: ±0.0, NaN, ±infinity
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- Precision boundaries and subnormal values
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- Mixed normal/edge case arrays
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### Status
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- [x] CI fixed (Rust 1.66 MSRV)
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- [x] Codebase analysis complete
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- [ ] Design FP comparison API
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- [ ] Implement core FP comparison logic
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- [ ] Add comprehensive tests
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- [ ] Create usage examples |