First draft of the NFA generator and dumper for the LTM system

sorear · Aug 12, 2010 · deb4f49 · deb4f49
1 parent 5d8b10e
commit deb4f49
Showing 1 changed file with 236 additions and 0 deletions.
diff --git a/Cursor.cs b/Cursor.cs
@@ -1,5 +1,6 @@
 using Niecza;
 using System;
+using System.Collections.Generic;
 // this exists to allow O(1) addition, since additions (esp. in the presence
 // of backtracking) dominate lookups
 
@@ -74,3 +75,238 @@ public class Cursor {
         return At(p);
     }
 }
+
+public sealed class CCTerm {
+    public readonly int category; // OR
+    public readonly char specific;
+
+    public readonly int denycatmask;
+    public readonly char[] denyspecific;
+    // todo: range stuff.
+
+    public CCTerm(int category, char specific, int denycatmask,
+            char[] denyspecific) {
+        this.category = category; this.specific = specific;
+        this.denycatmask = denycatmask; this.denyspecific = denyspecific;
+    }
+
+    public override string ToString() {
+        return new string(specific, 1); // TODO
+    }
+}
+
+public sealed class NFA {
+    public sealed class Node {
+        public int fate;
+        public bool final;
+        public List<Edge> edges = new List<Edge>();
+        public Node(int curfate) { fate = curfate; }
+
+        public override string ToString() {
+            System.Text.StringBuilder sb = new System.Text.StringBuilder();
+            sb.Append("(" + fate + ")" + (final ? "+" : ""));
+
+            foreach (Edge e in edges) {
+                sb.Append(", ");
+                sb.Append(e);
+            }
+
+            return sb.ToString();
+        }
+    }
+
+    public sealed class Edge {
+        public int to;
+        public CCTerm when; // null if epsilon
+
+        public override string ToString() {
+            return ((when != null) ? when.ToString() : "ε") + " => " + to;
+        }
+    }
+
+    public List<Node> nodes = new List<Node>();
+    public int curfate;
+
+    public int AddNode() {
+        nodes.Add(new Node(curfate));
+        return nodes.Count - 1;
+    }
+    public void AddEdge(int from, int to, CCTerm when) {
+        Edge e = new Edge();
+        e.to = to;
+        e.when = when;
+        nodes[from].edges.Add(e);
+    }
+
+    public void Dump() {
+        for (int ix = 0; ix < nodes.Count; ix++) {
+            Console.WriteLine(ix + ": " + nodes[ix].ToString());
+        }
+    }
+}
+
+// ltm automaton descriptors
+public abstract class LAD {
+    public abstract void ToNFA(NFA pad, int from, int to);
+    public abstract void Dump(int indent);
+    public virtual bool IsLiteral { get { return false; } }
+    public virtual int LiteralPrefixLength { get { return 0; } }
+}
+
+public class LADStr : LAD {
+    public readonly string text;
+    public LADStr(string text) { this.text = text; }
+
+    public override bool IsLiteral { get { return true; } }
+    public override int LiteralPrefixLength { get { return text.Length; } }
+
+    public override void ToNFA(NFA pad, int from, int to) {
+        if (text.Length == 0) {
+            pad.AddEdge(from, to, null);
+        } else {
+            int len = text.Length;
+            for (int c = 0; c < len; c++) {
+                int fromp = (c == len - 1) ? to : pad.AddNode();
+                pad.AddEdge(from, fromp, new CCTerm(-1, text[c], 0, null));
+                from = fromp;
+            }
+        }
+    }
+
+    public override void Dump(int indent) {
+        Console.WriteLine(new string(' ', indent) + "str: " + text);
+    }
+}
+
+public class LADStar : LAD {
+    public readonly LAD child;
+    public LADStar(LAD child) { this.child = child; }
+
+    public override void ToNFA(NFA pad, int from, int to) {
+        int knot = pad.AddNode();
+        pad.AddEdge(from, knot, null);
+        pad.AddEdge(knot, to, null);
+        child.ToNFA(pad, knot, knot);
+    }
+
+    public override void Dump(int indent) {
+        Console.WriteLine(new string(' ', indent) + "star:");
+        child.Dump(indent + 4);
+    }
+}
+
+public class LADOpt : LAD {
+    public readonly LAD child;
+    public LADOpt(LAD child) { this.child = child; }
+
+    public override void ToNFA(NFA pad, int from, int to) {
+        pad.AddEdge(from, to, null);
+        child.ToNFA(pad, from, to);
+    }
+
+    public override void Dump(int indent) {
+        Console.WriteLine(new string(' ', indent) + "opt:");
+        child.Dump(indent + 4);
+    }
+}
+
+public class LADPlus : LAD {
+    public readonly LAD child;
+    public LADPlus(LAD child) { this.child = child; }
+
+    public override bool IsLiteral { get { return child.IsLiteral; } }
+    public override int LiteralPrefixLength { get { return child.LiteralPrefixLength; } }
+
+    public override void ToNFA(NFA pad, int from, int to) {
+        int knot1 = pad.AddNode();
+        int knot2 = pad.AddNode();
+        pad.AddEdge(from, knot1, null);
+        pad.AddEdge(knot2, to, null);
+        pad.AddEdge(knot2, knot1, null);
+        child.ToNFA(pad, knot1, knot2);
+    }
+
+    public override void Dump(int indent) {
+        Console.WriteLine(new string(' ', indent) + "plus:");
+        child.Dump(indent + 4);
+    }
+}
+
+public class LADSequence : LAD {
+    public readonly LAD fst;
+    public readonly LAD snd;
+    public LADSequence(LAD fst, LAD snd) { this.fst = fst; this.snd = snd; }
+
+    public override bool IsLiteral {
+        get { return fst.IsLiteral && snd.IsLiteral; }
+    }
+
+    public override int LiteralPrefixLength {
+        get {
+            return fst.IsLiteral ?
+                (fst.LiteralPrefixLength + snd.LiteralPrefixLength) :
+                snd.LiteralPrefixLength;
+        }
+    }
+
+    public override void ToNFA(NFA pad, int from, int to) {
+        int knot = pad.AddNode();
+        fst.ToNFA(pad, from, knot);
+        snd.ToNFA(pad, knot, to);
+    }
+
+    public override void Dump(int indent) {
+        Console.WriteLine(new string(' ', indent) + "seq:");
+        fst.Dump(indent + 4);
+        snd.Dump(indent + 4);
+    }
+}
+
+public class Lexer {
+    public LAD[] alts;
+    public NFA pad = new NFA();
+    public string tag;
+
+    public static bool LtmTrace = true;
+
+    public Lexer(string tag, LAD[] alts) {
+        this.alts = alts;
+        this.tag = tag;
+        int root = pad.AddNode();
+        int[] alt_shuffle = new int[alts.Length];
+        for (int i = 0; i < alts.Length; i++) alt_shuffle[i] = i;
+        Array.Sort(alt_shuffle, delegate (int i1, int i2) {
+            int j1 = alts[i1].LiteralPrefixLength;
+            int j2 = alts[i2].LiteralPrefixLength;
+            return (j1 != j2) ? (j2 - j1) : (i1 - i2);
+        });
+        for (int ix = 0; ix < alts.Length; ix++) {
+            pad.curfate = alt_shuffle[ix];
+            int target = pad.AddNode();
+            pad.nodes[target].final = true;
+            alts[alt_shuffle[ix]].ToNFA(pad, root, target);
+        }
+        // now the NFA nodes are all in tiebreak order by lowest index
+        if (LtmTrace) {
+            Dump();
+        }
+    }
+
+    public void Dump() {
+        Console.WriteLine("--- LEXER ({0}) : Tree", tag);
+        for (int ix = 0; ix < alts.Length; ix++) {
+            Console.WriteLine("{0}:", ix);
+            alts[ix].Dump(0);
+        }
+        Console.WriteLine("--- NFA:");
+        pad.Dump();
+        Console.WriteLine("--- END");
+    }
+
+    public static void SelfTest() {
+        new Lexer("[for|forall]", new LAD[] {
+                new LADStr("for"),
+                new LADStr("forall"),
+            });
+    }
+}