[08 - AST] First implementations of Abstract Syntax Tree parsing

2020-05-18 12:21:35 +02:00
parent 8cf57691dc
commit dba220ceb8
2 changed files with 285 additions and 0 deletions
--- a/X-Leer/src/de/dhbw/compiler/xparser/ASTParser.java
+++ b/X-Leer/src/de/dhbw/compiler/xparser/ASTParser.java
@@ -1,5 +1,8 @@
 package de.dhbw.compiler.xparser;

+import java.util.LinkedList;
+import java.util.List;
+
 import de.dhbw.compiler.xparser.api.Parser;

 /**
@@ -13,6 +16,286 @@ public class ASTParser extends Parser {

    @Override
    public Tree parseProgram() {
+        int oldPosition = in.getPosition();
+        Tree program, id, decList, statList;
+
+        if ((program = parseToken(Token.PROGRAM)) != null
+            && (id = parseToken(Token.ID)) != null
+            && parseToken(Token.SEMICOLON) != null
+            && (decList = parseDecList()) != null
+            && (statList = parseStatList()) != null
+            && parseToken(Token.DOT) != null
+            && parseToken(Token.EOF) != null) {
+            Tree tree = new Tree(program.getToken());
+            tree.addLastChild(id);
+            tree.addLastChild(decList);
+            tree.addLastChild(statList);
+            return tree;
+        }
+
+        System.out.println("parseProgram> Skipping Tree");
+        in.setPosition(oldPosition);
        return null;
    }
+
+    private Tree parseStatList() {
+        Tree tree = new Tree(new Token(Token.STATLIST));
+        Tree stat;
+
+        while ((stat = parseStatWithSemicolon()) != null) {
+            tree.addLastChild(stat);
+        }
+        return tree;
+    }
+
+    private Tree parseStatWithSemicolon() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.STATWITHSEMI));
+        Tree state, semicolon;
+
+        if (((state = parseStat()) != null)
+            && ((semicolon = parseToken(Token.SEMICOLON)) != null)) {
+            tree.addLastChild(state);
+            tree.addLastChild(semicolon);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private Tree parseStat() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.STAT));
+        Tree numAssign, condStat, block;
+
+        if ((numAssign = parseNumAssign()) != null) {
+            tree.addLastChild(numAssign);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        if ((condStat = parseCondStat()) != null) {
+            tree.addLastChild(condStat);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        if ((block = parseBlock()) != null) {
+            tree.addLastChild(block);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private Tree parseCondStat() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.CONDSTAT));
+        Tree ifKey, cond, then, stat1, elseKey, stat2;
+
+        if ((ifKey = parseToken(Token.IF)) != null
+            && (cond = parseCond()) != null
+            && (then = parseToken(Token.THEN)) != null
+            && (stat1 = parseStat()) != null
+            && (elseKey = parseToken(Token.ELSE)) != null
+            && (stat2 = parseStat()) != null) {
+
+            tree.addLastChild(ifKey);
+            tree.addLastChild(cond);
+            tree.addLastChild(then);
+            tree.addLastChild(stat1);
+            tree.addLastChild(elseKey);
+            tree.addLastChild(stat2);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        if (((ifKey = parseToken(Token.IF)) != null)
+            && (cond = parseCond()) != null
+            && (then = parseToken(Token.THEN)) != null
+            && (stat1 = parseStat()) != null) {
+            tree.addLastChild(ifKey);
+            tree.addLastChild(cond);
+            tree.addLastChild(then);
+            tree.addLastChild(stat1);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private Tree parseCond() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.COND));
+        Tree a, operator, b;
+
+        if ((a = parseNumExpr()) != null
+            && ((operator = parseToken(Token.EQUALS)) != null
+                || (operator = parseToken(Token.LESS)) != null
+                || (operator = parseToken(Token.MORE)) != null)
+            && (b = parseNumExpr()) != null) {
+            tree.addLastChild(a);
+            tree.addLastChild(operator);
+            tree.addLastChild(b);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private Tree parseNumAssign() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.ASSIGNSTAT));
+        Tree id, assign, numExpr;
+
+        if ((id = parseToken(Token.ID)) != null
+            && (assign = parseToken(Token.ASSIGN)) != null
+            && (numExpr = parseNumExpr()) != null) {
+            tree.addLastChild(id);
+            tree.addLastChild(assign);
+            tree.addLastChild(numExpr);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private Tree parseNumExpr() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.EXPR));
+        Tree a, b, operator;
+
+        if (((a = parseNumExpr2()) != null)
+            && (((operator = parseToken(Token.PLUS)) != null
+                 || (operator = parseToken(Token.MINUS)) != null))
+            && (b = parseNumExpr()) != null) {
+            tree.addLastChild(a);
+            tree.addLastChild(operator);
+            tree.addLastChild(b);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        if ((a = parseNumExpr2()) != null) {
+            tree.addLastChild(a);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        return null;
+    }
+
+    private Tree parseNumExpr2() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.EXPR2));
+        Tree a, b, operator;
+
+        if (((a = parseNumExpr3()) != null)
+            && (((operator = parseToken(Token.MULT)) != null
+                 || (operator = parseToken(Token.DIV)) != null))
+            && (b = parseNumExpr2()) != null) {
+            tree.addLastChild(a);
+            tree.addLastChild(operator);
+            tree.addLastChild(b);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        if ((a = parseNumExpr3()) != null) {
+            tree.addLastChild(a);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        return null;
+    }
+
+    private Tree parseNumExpr3() {
+        int oldPosition = in.getPosition();
+        Tree tree = new Tree(new Token(Token.EXPR3));
+        Tree sign, intConst, id, num, lbr, rbr;
+
+        if ((intConst = parseToken(Token.INTCONST)) != null) {
+            tree.addLastChild(intConst);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        if (((sign = parseToken(Token.MINUS)) != null
+             && ((intConst = parseToken(Token.INTCONST))) != null)) {
+            tree.addLastChild(sign);
+            tree.addLastChild(intConst);
+            return tree;
+        }
+        in.setPosition(oldPosition);
+
+        if ((id = parseToken(Token.ID)) != null) {
+            tree.addLastChild(id);
+            return tree;
+        }
+
+        if (((lbr = parseToken(Token.LBR)) != null) && ((num = parseNumExpr()) != null)
+            && ((rbr = parseToken(Token.RBR)) != null)) {
+
+            tree.addLastChild(lbr);
+            tree.addLastChild(num);
+            tree.addLastChild(rbr);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private Tree parseDecList() {
+        Tree decList = new Tree(new Token(Token.DECLLIST));
+        Tree dec;
+
+        while ((dec = parseDec()) != null) {
+            decList.addLastChild(dec);
+        }
+
+        return decList;
+    }
+
+    private Tree parseDec() {
+        int oldPosition = in.getPosition();
+        Tree id, type;
+        List<Tree> modifiers = parseModifier();
+
+        if ((id = parseToken(Token.ID)) != null
+            && (parseToken(Token.COLON)) != null
+            && (type = parseToken(Token.TYPE)) != null) {
+            Tree tree = new Tree(new Token(Token.DECL));
+            tree.addLastChildren(modifiers);
+            tree.addLastChild(id);
+            tree.addLastChild(type);
+            return tree;
+        }
+
+        in.setPosition(oldPosition);
+        return null;
+    }
+
+    private List<Tree> parseModifier() {
+        int oldPosition = in.getPosition();
+        List<Tree> treeList = new LinkedList<>();
+        Tree read, print;
+
+        if ((read = parseToken(Token.READ)) != null) {
+            treeList.add(read);
+        }
+
+        if ((print = parseToken(Token.PRINT)) != null) {
+            treeList.add(print);
+        }
+
+        return treeList;
+    }
+
 }
--- a/X-Leer/src/de/dhbw/compiler/xparser/Tree.java
+++ b/X-Leer/src/de/dhbw/compiler/xparser/Tree.java
@@ -32,6 +32,8 @@ public class Tree {
 		this.children.addLast(child);
 	}

+	public void addLastChildren(List<Tree> children) { this.children.addAll(children); }
+	
 	public void addFirstChild(Tree child) {
 		this.children.addFirst(child);
 	}