CallSharp: Automatic Input/Output Matching in .NET

CallSharp: Automatic Input/Output Matching in .NET

• 1.
  CallSharp: Automatic Input/Output Matchingin .NET Dmitri Nesteruk @dnesteruk
• 2.
  The Problem Given inputand required output data, use “artificial intelligence” to determine the call, or chain of calls, that would lead to the output. "abc" ⟶ "cba" new string(input.Reverse().ToArray())
• 3.
  → “abc” is clearlya String Strings are immutable (pure functions) Look for any member function (property) that Is a member of String Has no arguments Returns a String Very simple search abc ABC
• 4.
  String-to-String Methods Normalize ToLower ToLowerInvariant ToUpper ToUpperInvariant ToString Trim TrimStart TrimEnd Functions thattake no arguments Functions where all arguments have default values Functions that take a single argument of type params[]
• 5.
  → input.ToUpper() input.ToUpperInvariant() abc ABC
• 6.
  → • A problem! •What is “3”? • Definitely a string (everything is) • Parses as integral type… • Also a floating-point type • Even a TimeSpan! • Let the user choose (assume Int32) • Search for String member functions yielding Int32 abc 3
• 7.
  → input.Length abc 3
• 8.
  → • Output iseither a bool or a String • Let’s assume bool for the time being • String has only one bool-returning function • IsNormalized() = true • But String also has static functions, so… • Search all static String-returning functions abc false
• 9.
  → string.IsNullOrEmpty(input) string.IsNullOrWhiteSpace(input) abc false
• 10.
  → Try all singlestatic/non-static calls… no luck Try a call chain String 𝑓𝑓() String 𝑔𝑔() String T → U → T T → U → V → T etc. Also includes constructor calls Complexity explosion Beware of implicit conversions abc⎵⎵ ABC
• 11.
  → string.Concat(input.Split()).ToUpper() string.Concat(input.Split()).ToUpperInvariant() input.ToUpper().Trim() input.ToUpper().TrimEnd() input.ToUpperInvariant().Trim() input.ToUpperInvariant().TrimEnd() input.Trim().ToUpper() input.Trim().ToUpperInvariant() input.TrimEnd().ToUpperInvariant() input.TrimEnd().ToUpper() // +lots more solutions abc⎵⎵ ABC
• 12.
  → • We needto trim away ‘b’ • ‘b’ is a substring of “aaabbb” (one of many) • String can be decomposed into characters • These can be used on their own; or • Combinations lumped together to form strings • Look for member/static functions which • Take a single object of some type that String can be decomposed into (string or char) • Take multiple parameters (ordinary or params[]) aaabbb aaa
• 13.
  → input.Trim('b') input.TrimEnd('b') aaabbb aaa
• 14.
  → input.Trim('e','r') input.Trim('r','e') input.Trim('a','e','r') input.Trim('a','r','e') input.Trim('e','a','r') input.Trim('e','r','a') input.Trim('r','a','e') input.Trim('r','e','a') input.TrimEnd('e','r') input.TrimEnd('r','e') // 30+ moreoptions cater cat Commutativity Sufficiency
• 15.
  → input.Replace("aabb", "aa") input.Replace("bb", "") input.Replace("bbcc","cc") aabbcc aacc Search all possible pairs of arguments Middle option is least redundant
• 16.
  → input.Replace(" ", string.Empty) input.Replace("b ", "b") input.Replace("a b ", "ab") input.Replace(" b c", "bc") input.Replace("a b c", "abc") // at greater depth, string.Concat(input.Split()) a⎵b⎵c abc Only the first option is fundamentally correct
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  Performance Reflection • MethodInfo.Invoke() isvery expensive • Delegate.CreateDelegate() only viable for static methods • Most investigated types are core CLR ones Complexity explosion (near-infinite in certain cases)
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  Summary Exhausive search forsingle non/static calls Search for call chains Argument combinations/permutations
• 19.
  Feature Improvements Operator support(e.g., op[]) Sequence handling (array/list/IEnumerable) Regular expression inference (e.g., Regex.Replace) Other programming languages 
• 20.
  Performance Improvements Static reflectionfor known types (T4) Better search (annealing etc.) Emulated evaluation of complex searches (GPU?) Distributed/cloud back-end
• 21.
  Summary CallSharp is open-source Youcan help! http://github.com/nesteruk/callsharp Skype: dmitri.nesteruk @dnesteruk