[DRAFT] Experimental conversion of Regex to BNF

Package.swift

@@ -135,6 +135,13 @@ let package = Package(
                 "_RegexParser",
                 "_StringProcessing"
             ]),
+        .executableTarget(
+            name: "Regex2BNF",
+            dependencies: [
+                .product(name: "ArgumentParser", package: "swift-argument-parser"),
+                "_RegexParser"
+            ],
+            swiftSettings: [availabilityDefinition]),
         .executableTarget(
             name: "RegexTester",
             dependencies: [

Sources/Regex2BNF/Regex2BNF.swift

@@ -0,0 +1,89 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import ArgumentParser
+import _RegexParser
+
+@main
+@available(SwiftStdlib 5.8, *)
+struct Regex2BNF: ParsableCommand {
+  @Argument(help: "The regex pattern to convert to BNF.")
+  var pattern: String
+
+  @Flag(
+    name: [.customShort("e"), .customLong("examples")],
+    help: "Run several examples")
+  var runExamples = false
+
+  func convert(_ pattern: String) throws {
+    print("/\(pattern)/\n")
+    print(try _printAsBNF(inputRegex: pattern))
+  }
+
+  mutating func run() throws {
+    if runExamples {
+      // TODO: Turn into test cases
+//      print("[Examples")
+
+//      print("Single-scalar character literals:")
+      try convert("a")
+      try convert("Z")
+      try convert("あ")
+      try convert("日")
+      try convert("\u{301}")
+
+
+//      print("Multi-scalar character literals")
+      try convert("🧟‍♀️")
+      try convert("e\u{301}")
+
+//      print("Simple alternations")
+      try convert("a|b")
+      try convert("a|b|c|d")
+      try convert("a|🧟‍♀️\u{301}日|z")
+
+//      print("Simple quantifications")
+      try convert("a*")
+      try convert("a+")
+      try convert("a?")
+      try convert("a{2,10}")
+      try convert("a{,10}")
+      try convert("a{2,}")
+
+//      print("Grouping")
+      try convert("a(b|c)d")
+      try convert("a(?:b|c)d")
+      try convert("a(bcd|def(g|h)+)z")
+
+//      print("Dot")
+      try convert(".*")
+      try convert("(a|b)*.{3}(a|b)")
+
+//      print("Bultin character classes")
+      try convert(#"\(\d{3}\)\d{3}-\d{4}"#)
+      try convert(#"\s+keyword\s+"#)
+
+
+//      print("[Done]")
+
+      // Look at optimizer output, the quant child is very long
+      try convert("a(123456789)+b")
+
+      try convert("Hi the time right now is (AM|PM)")
+
+      try convert("a(b|c)*d{2,4}e?")
+    }
+    try convert(pattern)
+
+
+
+  }
+}

Sources/RegexBenchmark/BenchmarkChart.swift

@@ -1,80 +1,80 @@
-//===----------------------------------------------------------------------===//
+////===----------------------------------------------------------------------===//
+////
+//// This source file is part of the Swift.org open source project
+////
+//// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
+//// Licensed under Apache License v2.0 with Runtime Library Exception
+////
+//// See https://swift.org/LICENSE.txt for license information
+////
+////===----------------------------------------------------------------------===//
 //
-// This source file is part of the Swift.org open source project
+//#if os(macOS) && canImport(Charts)
 //
-// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
-// Licensed under Apache License v2.0 with Runtime Library Exception
+//import Charts
+//import SwiftUI
 //
-// See https://swift.org/LICENSE.txt for license information
+//struct BenchmarkChart: View {
+//  var comparisons: [BenchmarkResult.Comparison]
 //
-//===----------------------------------------------------------------------===//
-
-#if os(macOS) && canImport(Charts)
-
-import Charts
-import SwiftUI
-
-struct BenchmarkChart: View {
-  var comparisons: [BenchmarkResult.Comparison]
-
-  // Sort by normalized difference
-  var sortedComparisons: [BenchmarkResult.Comparison] {
-    comparisons.sorted { a, b in
-      a.normalizedDiff < b.normalizedDiff
-    }
-  }
-  var body: some View {
-    VStack(alignment: .leading) {
-      Chart {
-        ForEach(sortedComparisons) { comparison in
-          // Normalized runtime
-          BarMark(
-            x: .value("Name", comparison.name),
-            y: .value("Normalized runtime", comparison.normalizedDiff))
-          .foregroundStyle(LinearGradient(
-            colors: [.accentColor, comparison.diff?.seconds ?? 0 <= 0 ? .green : .yellow],
-            startPoint: .bottom,
-            endPoint: .top))
-        }
-        // Baseline
-        RuleMark(y: .value("Time", 1.0))
-        .foregroundStyle(.red)
-        .lineStyle(.init(lineWidth: 1, dash: [2]))
-        .annotation(position: .top, alignment: .leading) {
-          Text("Baseline").foregroundStyle(.red)
-        }
-
-      }
-      .frame(idealWidth: 800, idealHeight: 800)
-      .chartYScale(domain: 0...2.0)
-      .chartYAxis {
-        AxisMarks(values: .stride(by: 0.1))
-      }
-      .chartXAxis {
-        AxisMarks { value in
-          AxisGridLine()
-          AxisTick()
-          AxisValueLabel(value.as(String.self)!, orientation: .vertical)
-        }
-      }
-    }
-  }
-}
-
-struct BenchmarkResultApp: App {
-  static var comparisons: [BenchmarkResult.Comparison]?
-
-  var body: some Scene {
-    WindowGroup {
-      if let comparisons = Self.comparisons {
-        ScrollView {
-          BenchmarkChart(comparisons: comparisons)
-        }
-      } else {
-        Text("No data")
-      }
-    }
-  }
-}
-
-#endif
+//  // Sort by normalized difference
+//  var sortedComparisons: [BenchmarkResult.Comparison] {
+//    comparisons.sorted { a, b in
+//      a.normalizedDiff < b.normalizedDiff
+//    }
+//  }
+//  var body: some View {
+//    VStack(alignment: .leading) {
+//      Chart {
+//        ForEach(sortedComparisons) { comparison in
+//          // Normalized runtime
+//          BarMark(
+//            x: .value("Name", comparison.name),
+//            y: .value("Normalized runtime", comparison.normalizedDiff))
+//          .foregroundStyle(LinearGradient(
+//            colors: [.accentColor, comparison.diff?.seconds ?? 0 <= 0 ? .green : .yellow],
+//            startPoint: .bottom,
+//            endPoint: .top))
+//        }
+//        // Baseline
+//        RuleMark(y: .value("Time", 1.0))
+//        .foregroundStyle(.red)
+//        .lineStyle(.init(lineWidth: 1, dash: [2]))
+//        .annotation(position: .top, alignment: .leading) {
+//          Text("Baseline").foregroundStyle(.red)
+//        }
+//        
+//      }
+//      .frame(idealWidth: 800, idealHeight: 800)
+//      .chartYScale(domain: 0...2.0)
+//      .chartYAxis {
+//        AxisMarks(values: .stride(by: 0.1))
+//      }
+//      .chartXAxis {
+//        AxisMarks { value in
+//          AxisGridLine()
+//          AxisTick()
+//          AxisValueLabel(value.as(String.self)!, orientation: .vertical)
+//        }
+//      }
+//    }
+//  }
+//}
+//
+//struct BenchmarkResultApp: App {
+//  static var comparisons: [BenchmarkResult.Comparison]?
+//
+//  var body: some Scene {
+//    WindowGroup {
+//      if let comparisons = Self.comparisons {
+//        ScrollView {
+//          BenchmarkChart(comparisons: comparisons)
+//        }
+//      } else {
+//        Text("No data")
+//      }
+//    }
+//  }
+//}
+//
+//#endif

Sources/RegexBenchmark/BenchmarkResults.swift

@@ -114,16 +114,16 @@ extension BenchmarkRunner {
       print(item)
     }
 
-    #if os(macOS) && canImport(Charts)
-    if showChart {
-      print("""
-        === Comparison chart =================================================================
-        Press Control-C to close...
-        """)
-      BenchmarkResultApp.comparisons = comparisons
-      BenchmarkResultApp.main()
-    }
-    #endif
+//    #if os(macOS) && canImport(Charts)
+//    if showChart {
+//      print("""
+//        === Comparison chart =================================================================
+//        Press Control-C to close...
+//        """)
+//      BenchmarkResultApp.comparisons = comparisons
+//      BenchmarkResultApp.main()
+//    }
+//    #endif
   }
 
   func saveComparisons(