week6 ennustavate parserite lahendused

Author: sim642

sols/week6/parsers/mini/AbbaParser.java

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+package week6.parsers.mini;
+
+import week6.parsers.Node;
+import week6.parsers.Parser;
+
+// S → ABAR
+// A → a | aAb
+// B → bb | BbSb
+// R → +S | ε
+public class AbbaParser extends Parser {
+
+    public AbbaParser(String input) {
+        super(input);
+    }
+
+    // S → ABAR
+    @Override
+    protected Node s() {
+        Node n = new Node('S');
+        n.add(a());
+        n.add(b());
+        n.add(a());
+        n.add(r());
+        return n;
+    }
+
+    // A → a(Ab|ε)
+    private Node a() {
+        Node n = new Node('A');
+        n.add(match('a'));
+        switch (peek()) {
+            case 'a':
+                n.add(a());
+                n.add(match('b'));
+                break;
+            case 'b':
+            case '$':
+            case '+':
+                break;
+            default:
+                expected('a', 'b', '$', '+');
+        }
+        return n;
+    }
+    
+    // B → bbQ
+    private Node b() {
+        Node n = new Node('B');
+        n.add(match('b'));
+        n.add(match('b'));
+        return q(n);
+    }
+
+    // Q → bSbQ | ε
+    private Node q(Node b) {
+        switch (peek()) {
+            case 'b':
+                Node n = new Node('B');
+                n.add(b);
+                n.add(match('b'));
+                n.add(s());
+                n.add(match('b'));
+                return q(n);
+            case 'a':
+                return b;
+            default:
+                expected('a', 'b');
+                return null;
+        }
+    }
+
+    // R → +S | ε
+    private Node r() {
+        Node n = new Node('R');
+        switch (peek()) {
+            case '+':
+                n.add(match('+'));
+                n.add(s());
+                break;
+            case 'b':
+            case '$':
+                n.add(epsilon());
+                break;
+            default:
+                expected('+', '$', 'b');
+        }
+        return n;
+    }
+
+    public static Node parse(String src) {
+        AbbaParser parser = new AbbaParser(src);
+        return parser.parse();
+    }
+
+    static void main() {
+        AbbaParser parser = new AbbaParser("abba");
+        parser.testParser();
+    }
+
+}

sols/week6/parsers/mini/AktParser.java

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+package week6.parsers.mini;
+
+import week6.parsers.Node;
+import week6.parsers.Parser;
+
+// S → AkT
+// A -> aA | ε
+// T -> t | tSp | Tt
+// R -> tR | ε
+public class AktParser extends Parser {
+
+    public AktParser(String input) {
+        super(input);
+    }
+
+    // S → AkT
+    @Override
+    protected Node s() {
+        Node n = new Node('S');
+        n.add(a());
+        n.add(match('k'));
+        n.add(t());
+        return n;
+    }
+
+    // A -> aA | ε
+    private Node a() {
+        Node n = new Node('A');
+        switch (peek()) {
+            case 'a':
+                n.add(match('a'));
+                n.add(a());
+                break;
+            case 'k':
+                n.add(epsilon());
+                break;
+            default:
+                expected('a', 'k');
+        }
+        return n;
+    }
+
+    //  T -> t | tSp | Tt
+    //  T -> t (SP|ε) R
+    private Node t() {
+        Node n = new Node('T');
+        n.add(match('t'));
+        switch (peek()) {
+            case 'a':
+            case 'k':
+                n.add(s());
+                n.add(match('p'));
+                break;
+            case 'p':
+            case 't':
+            case '$':
+                break;
+            default:
+                expected('a','k','p','t','$');
+        }
+        return r(n);
+    }
+
+    // R -> tR | ε
+    private Node r(Node n) {
+        switch (peek()) {
+            case 't':
+                Node t = new Node('T');
+                t.add(n);
+                t.add(match('t'));
+                return r(t);
+            case 'p':
+            case '$':
+                return n;
+            default:
+                expected('t', 'p', '$');
+        }
+        return null;
+    }
+
+    public static Node parse(String src) {
+        AktParser parser = new AktParser(src);
+        return parser.parse();
+    }
+
+}
+

sols/week6/parsers/mini/BoratParser.java

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+package week6.parsers.mini;
+
+import week6.parsers.Node;
+import week6.parsers.Parser;
+
+
+// S → AB
+// A → boA | baA | ε
+// B → Blo | Bbi | rat
+public class BoratParser extends Parser {
+
+    public BoratParser(String input) {
+        super(input);
+    }
+
+    // S → AB
+    @Override
+    protected Node s() {
+        Node n = new Node('S');
+        n.add(a());
+        n.add(b());
+        return n;
+    }
+
+    // A → b(o|a)A | ε
+    private Node a() {
+        Node n = new Node('A');
+        switch (peek()) {
+            case 'b':
+                n.add(match('b'));
+                switch (peek()) {
+                    case 'o' -> n.add(match('o'));
+                    case 'a' -> n.add(match('a'));
+                    default -> expected('o', 'a');
+                }
+                n.add(a());
+                break;
+            case 'r':
+                n.add(epsilon());
+                break;
+            default:
+                expected('b', 'r');
+        }
+        return n;
+    }
+
+    //  B → rat R
+    private Node b() {
+        Node n = new Node('B');
+        n.add(match('r'));
+        n.add(match('a'));
+        n.add(match('t'));
+        return r(n);
+    }
+
+    // R → biR | loR | ε
+    private Node r(Node n) {
+        Node b = new Node('B');
+        b.add(n);
+        switch (peek()) {
+            case 'l':
+                b.add(match('l'));
+                b.add(match('o'));
+                return r(b);
+            case 'b':
+                b.add(match('b'));
+                b.add(match('i'));
+                return r(b);
+            case '$':
+                return n;
+            default:
+                expected('l', 'b', '$');
+        }
+        return null;
+    }
+
+    public static Node parse(String src) {
+        BoratParser parser = new BoratParser(src);
+        return parser.parse();
+    }
+
+}
+