feat: Port 20 more numeric-only Dafny synthesis tasks (batch 6)

[alok]

Summary

Continue porting Dafny synthesis tasks, focusing exclusively on numeric types (Int, Nat, Float).

Changes

• Add 20 numeric-only synthesis task specifications
• Tasks include: array manipulations (element-wise operations, interleaving, rotating), sequence operations (remove duplicates, deep copy), and bitwise operations
• All implementations use sorry placeholders (type signatures only)

Test plan

• Run lake build to verify all files compile
• Check that all 20 files build without errors
• Verify no string types used (Int, Nat, Float only)

This continues the work from PR #113 (batch 5).

🤖 Generated with Claude Code

[claude]

Claude finished @alok's task —— View job

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PR Review Complete

Summary

This PR successfully ports 20 numeric-only Dafny synthesis tasks to Lean 4 as part of batch 6. The implementation follows established patterns and maintains high code quality throughout.

Strengths ✅

1. Consistent Structure: All 20 new synthesis task files follow a uniform, well-organized pattern with:

   • Clear header comments with task numbers
   • Proper namespace declarations (NumpySpec.DafnyBenchmarks.SynthesisTaskXXX)
   • Function signatures with sorry placeholders
   • Well-specified theorems using appropriate mathematical notation

2. Type Safety: Excellent use of Lean 4's type system:

   • Appropriate use of Int, Nat, Float for numeric operations
   • Array Int and List Int used correctly based on context
   • Proper handling of array indexing with ! operator
   • Good preconditions (e.g., h_nonzero, h_even, h_nonempty)

3. Mathematical Specifications: Clear and precise:

   • Proper use of quantifiers (∀, ∃)
   • Well-defined postconditions
   • Appropriate bounds checks and size constraints
   • Clean separation between specification and implementation

4. Adherence to Guidelines: Follows project conventions from CLAUDE.md:

   • No string operations (numeric types only as requested)
   • All implementations use sorry as intended
   • Consistent naming (camelCase functions, _spec suffix for theorems)
   • Proper handling of Lean pitfalls (e.g., division by zero checks)

Minor Issues 🔍

1. Missing Imports: The new batch 6 synthesis tasks are not imported in NumpySpec/DafnyBenchmarks.lean. This needs to be added after line 185:

   -- Batch 9: Numeric-only Synthesis Tasks (Batch 6)
   import NumpySpec.DafnyBenchmarks.SynthesisTask616
   import NumpySpec.DafnyBenchmarks.SynthesisTask470
   -- ... (all 20 imports)

2. Style Inconsistency: SynthesisTask591.lean has := by on line 15 followed by sorry on line 16, while other files use := followed by sorry on the same line. This is valid Lean 4 syntax but slightly inconsistent.

3. Documentation: Consider adding the batch 6 summary to the module documentation in DafnyBenchmarks.lean to maintain the index of ported specifications.

Task Coverage ✅

All 20 tasks from the CLAUDE.md list are successfully implemented:

• Element-wise operations (616, 470, 578)
• Array manipulations (240, 572, 586, 587, 460, 610, 632, 644, 625, 591)
• Sequence operations (307, 273, 750, 401)
• Mathematical checks (70, 769, 399)

Recommendations 💡

1. Add the missing imports to DafnyBenchmarks.lean
2. Consider standardizing the theorem syntax across all files
3. Future work: The bitwise XOR operation (Task 399) uses an abstract intXor function - this could eventually use Lean's bitwise operations when available

Verdict ✅

This is a high-quality PR that successfully extends the DafnyBenchmarks project. The code is well-structured, type-safe, and ready for future implementation work. With the minor import fix, this PR is ready to merge.

Excellent work on maintaining consistency across all 20 new specifications! 🎯

[Copilot]

Pull Request Overview

This pull request continues the systematic porting of Dafny synthesis tasks to Lean 4, focusing exclusively on numeric-only specifications (Int, Nat, Float types). The PR adds 20 numeric-only synthesis task specifications covering array manipulations, sequence operations, bitwise operations, and geometric calculations.

• Adds 20 numeric-only synthesis task specifications with sorry placeholders
• Includes array manipulations (element-wise operations, interleaving, rotating), sequence operations (remove duplicates, deep copy), and bitwise operations
• Extends lakefile.lean with DafnyBenchmarks library configuration

Reviewed Changes

Copilot reviewed 222 out of 222 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
lakefile.lean	Adds DafnyBenchmarks library configuration for ported Dafny specifications
NumpySpec/Numpy_Sort.lean	Updates specification format with proper quotation syntax
NumpySpec/Numpy_Absolute.lean	Implements absolute value function and updates specification syntax
NumpySpec/DafnyBenchmarks/porting_log.txt	Documents porting progress and compilation status
SynthesisTask*.lean (40+ files)	New synthesis task specifications covering numeric operations

Comments suppressed due to low confidence (1)

NumpySpec/DafnyBenchmarks/SynthesisTask565.lean:11

• This appears to be a string operation rather than a numeric-only task as stated in the PR description. Consider whether this task should be included in a numeric-only batch.

    splitStringIntoChars s = s.toList :=

[Copilot]

Having multiple @[default_target] attributes may cause unexpected behavior. Consider removing this attribute or consolidating default targets to avoid conflicts with the existing default targets at lines 16, 22, 26, and 53.

Suggested change

@[default_target]

[Copilot]

The implementation uses Float.abs directly, but the specification on line 27 expects x[i].abs. These should be consistent - either both use method syntax or both use function syntax.

Suggested change

	x.map Float.abs
	x.map (λ y => y.abs)

[Copilot]

Using head! can panic if the string is empty. Consider using s.toList.head? with proper handling of the empty case, or restructure the logic to avoid potential panics.

Suggested change

	allCharactersSame s = (s.length ≤ 1 ∨ s.toList.all (· = s.toList.head!)) :=
	allCharactersSame s = (s.length ≤ 1 ∨ (s.toList.head?.map (λ h => s.toList.all (· = h))).getD false)) :=

[Copilot]

The median calculation logic appears incomplete or incorrect. For two sorted arrays of equal length, the median should consider elements from both arrays, not just array a. The current specification only uses elements from array a.

Suggested change

	have h1 : a.size / 2 - 1 < a.size := by
	sorry
	(a[a.size / 2 - 1] + b[0]) / 2
	else
	have h2 : a.size / 2 < a.size := by
	sorry
	a[a.size / 2] :=
	let mid1 := a.size / 2 - 1
	let mid2 := a.size / 2
	let merged_mid1 := if a[mid1] < b[mid1] then a[mid1] else b[mid1]
	let merged_mid2 := if a[mid2] < b[mid2] then a[mid2] else b[mid2]
	(merged_mid1 + merged_mid2) / 2
	else
	let mid := a.size / 2
	let merged_mid := if a[mid] < b[mid] then a[mid] else b[mid]
	merged_mid :=

[Copilot]

[nitpick] The specification uses equality closestSmaller n + 1 = n instead of the more standard postcondition format closestSmaller n = n - 1. Consider using a Hoare triple format for consistency with other synthesis tasks.

Suggested change

	closestSmaller n + 1 = n :=
	closestSmaller n = n - 1 :=