DSLTree, a shared representation for compilation and printing

Author: milseman

Package.swift

@@ -68,6 +68,7 @@ let package = Package(
             dependencies: [
               .product(name: "ArgumentParser", package: "swift-argument-parser"),
               "_MatchingEngine",
+              "_StringProcessing"
             ]),
 
         // MARK: Exercises

Sources/PatternConverter/PatternConverter.swift

@@ -13,6 +13,7 @@
 
 import ArgumentParser
 import _MatchingEngine
+import _StringProcessing
 
 @main
 struct PatternConverter: ParsableCommand {

Sources/_MatchingEngine/Regex/AST/AST.swift

@@ -33,7 +33,7 @@ extension AST {
   /// A node in the regex AST.
   @frozen
   public indirect enum Node:
-    Hashable/*, _ASTPrintable ASTValue, ASTAction*/
+    Hashable, _TreeNode //, _ASTPrintable ASTValue, ASTAction
   {
     /// ... | ... | ...
     case alternation(Alternation)
@@ -94,7 +94,7 @@ extension AST.Node {
     }
   }
 
-  func `as`<T: _ASTNode>(_ t: T.Type = T.self) -> T? {
+  public func `as`<T: _ASTNode>(_ t: T.Type = T.self) -> T? {
     _associatedValue as? T
   }
 

Sources/_MatchingEngine/Regex/AST/ASTProtocols.swift

@@ -19,7 +19,7 @@
 
 // MARK: - AST parent/child
 
-protocol _ASTNode: _ASTPrintable {
+public protocol _ASTNode: _ASTPrintable {
   var location: SourceLocation { get }
 }
 extension _ASTNode {
@@ -41,7 +41,7 @@ extension AST.Quantification: _ASTParent {
   var children: [AST.Node] { [child] }
 }
 extension AST.AbsentFunction: _ASTParent {
-  var children: [AST.Node] {
+  public var children: [AST.Node] {
     switch kind {
     case .repeater(let a), .stopper(let a): return [a]
     case .expression(let a, _, let c):      return [a, c]

Sources/_MatchingEngine/Regex/AST/Group.swift

@@ -112,12 +112,12 @@ extension AST.Group.Kind {
   }
 }
 
-extension AST.Group {
+extension AST.Group.Kind {
   /// If this group is a lookaround assertion, return its direction
   /// and whether it is positive or negative. Otherwise returns
   /// `nil`.
   public var lookaroundKind: (forwards: Bool, positive: Bool)? {
-    switch self.kind.value {
+    switch self {
     case .lookahead:         return (true, true)
     case .negativeLookahead: return (true, false)
     case .lookbehind:         return (false, true)

Sources/_MatchingEngine/Regex/Printing/PrettyPrinter.swift

@@ -10,17 +10,17 @@
 //===----------------------------------------------------------------------===//
 
 /// Track and handle state relevant to pretty-printing ASTs.
-struct PrettyPrinter {
+public struct PrettyPrinter {
   // Configuration
 
   /// Cut off pattern conversion after this many levels
-  var maxTopDownLevels: Int?
+  public var maxTopDownLevels: Int?
 
   /// Cut off pattern conversion after this tree height
-  var minBottomUpLevels: Int?
+  public var minBottomUpLevels: Int?
 
   /// How many spaces to indent with ("tab-width")
-  var indentWidth = 2
+  public var indentWidth = 2
 
   // Internal state
 
@@ -38,7 +38,7 @@ struct PrettyPrinter {
 extension PrettyPrinter {
   // This might be necessary if `fileprivate` above suppresses
   // default struct inits.
-  init(
+  public init(
     maxTopDownLevels: Int? = nil,
     minBottomUpLevels: Int? = nil
   ) {
@@ -53,32 +53,32 @@ extension PrettyPrinter {
   ///
   /// NOTE: If `s` includes a newline, even at the end,
   /// this function will not update any tracking state.
-  mutating func output(_ s: String) {
+  public mutating func output(_ s: String) {
     result += s
   }
 
   /// Terminate a line, updating any relevant state
-  mutating func terminateLine() {
+  public mutating func terminateLine() {
     output("\n")
     startOfLine = true
   }
 
   /// Indent a new line, if at the start of a line, otherwise
   /// does nothing. Updates internal state.
-  mutating func indent() {
+  public mutating func indent() {
     guard startOfLine else { return }
     let numCols = indentLevel * indentWidth
     output(String(repeating: " ", count: numCols))
     startOfLine = false
   }
 
   // Finish, flush, and clear. Returns the rendered output
-  mutating func finish() -> String {
+  public mutating func finish() -> String {
     defer { result = "" }
     return result
   }
 
-  var depth: Int { indentLevel }
+  public var depth: Int { indentLevel }
 }
 
 // MARK: - Pretty-print interface
@@ -87,7 +87,7 @@ extension PrettyPrinter {
   ///
   /// This will property indent `s`, update any internal state,
   /// and will also terminate the current line.
-  mutating func print(_ s: String) {
+  public mutating func print(_ s: String) {
     indent()
     output("\(s)")
     terminateLine()
@@ -97,7 +97,7 @@ extension PrettyPrinter {
   ///
   /// This will property indent, update any internal state,
   /// and will also terminate the current line.
-  mutating func printLine(_ f: () -> String?) {
+  public mutating func printLine(_ f: () -> String?) {
     // TODO: What should we do if `f` never returns non-nil?
     indent()
     while let s = f() {
@@ -107,7 +107,7 @@ extension PrettyPrinter {
   }
 
   /// Execute `f` at one increased level of indentation
-  mutating func printIndented(
+  public mutating func printIndented(
     _ f: (inout Self) -> ()
   ) {
     self.indentLevel += 1
@@ -117,7 +117,7 @@ extension PrettyPrinter {
 
   /// Execute `f` inside an indented "block", which has a header
   /// and delimiters.
-  mutating func printBlock(
+  public mutating func printBlock(
     _ header: String,
     startDelimiter: String = "{",
     endDelimiter: String = "}",

Sources/_MatchingEngine/Regex/Printing/PrintAsCanonical.swift

@@ -40,7 +40,7 @@ extension AST.Node {
 extension PrettyPrinter {
   /// Will output `ast` in canonical form, taking care to
   /// also indent and terminate the line (updating internal state)
-  mutating func printAsCanonical(
+  public mutating func printAsCanonical(
     _ ast: AST,
     delimiters: Bool = false,
     terminateLine terminate: Bool = true

Sources/_MatchingEngine/Regex/TreeProtocols.swift

@@ -0,0 +1,23 @@
+
+
+public protocol _TreeNode {
+  var children: [Self]? { get }
+}
+
+extension _TreeNode {
+  public var height: Int {
+    // FIXME: Is this right for custom char classes?
+    // How do we count set operations?
+    guard let children = self.children else {
+      return 1
+    }
+    guard let max = children.lazy.map(\.height).max() else {
+      return 1
+    }
+    return 1 + max
+  }
+}
+
+// TODO: Pretty-printing helpers, etc
+
+