#similarity.mbt

#Features

• AST-based comparison - Uses moonbitlang/parser to parse MoonBit code
• TSED Algorithm - Tree Structure Edit Distance for accurate structural similarity
• Function extraction - Extracts functions, methods, and tests from MoonBit source
• Cross-file detection - Compare functions across multiple files

#Installation

#CLI Tool

git clone https://github.com/mizchi/similarity.mbt
cd similarity.mbt
make install  # Installs to ~/.local/bin/similarity-mbt

#As a Library

{
  "deps": {
    "mizchi/similarity": "0.1.0"
  }
}

#Usage

#CLI

# Scan all .mbt files in current directory
similarity-mbt

# Scan specific files
similarity-mbt src/*.mbt

# Adjust threshold (default: 0.88)
similarity-mbt -t 0.95 *.mbt

# Exclude test files
similarity-mbt --no-tests

# Show help
similarity-mbt -h

#Basic similarity detection (Library)

let source =
  #|fn add(a : Int, b : Int) -> Int { a + b }
  #|fn sum(x : Int, y : Int) -> Int { x + y }

let options = @similarity.DetectorOptions::default()
let results = @similarity.detect_similarities(source, options)

for result in results {
  println(result)  // add <-> sum (similarity: 95%, score: 2.8)
}

#Custom options

///|
let options : @similarity.DetectorOptions = {
  threshold: 0.80, // Minimum similarity (0.0-1.0)
  min_lines: 3, // Minimum lines per function
  size_penalty: true, // Penalize size differences
}

#Cross-file comparison

let files = [
  ("file1.mbt", source1),
  ("file2.mbt", source2),
]
let results = @similarity.detect_cross_file_similarities(files, options)

for result in results {
  let (file1, file2, sim) = result
  println("\{file1}:\{sim.func1.name} <-> \{file2}:\{sim.func2.name}")
}

#Direct tree comparison

///|
let functions = @similarity.extract_functions(source)

///|
let tsed_options = @similarity.TSEDOptions::default()

///|
let similarity = @similarity.calculate_tsed(
  functions[0].tree,
  functions[1].tree,
  tsed_options,
)

#API

#Types

• DetectorOptions - Configuration for similarity detection
• FunctionInfo - Extracted function with name, line info, and AST tree
• SimilarityResult - Comparison result with similarity score
• TreeNode - AST tree node for TSED comparison

#Functions

• detect_similarities(source, options) - Detect similar functions in source
• detect_cross_file_similarities(sources, options) - Cross-file comparison
• extract_functions(source) - Extract functions from source code
• calculate_tsed(tree1, tree2, options) - Calculate tree edit distance

#Algorithm

1. Parse - Convert MoonBit source to AST using moonbitlang/parser
2. Extract - Extract function bodies as tree structures
3. Compare - Calculate edit distance between trees
4. Normalize - Apply size penalties and normalization

#License