The expression parser can now parse more than a simple expression

- Added sequencing (; and {}).
- Added =, +=, -=, *=, /=, %=, ^= to the expression parser. (left-associative for now, will change later)
- Added pre-increment(++) and pre-decrement(--) operators.
- Adjusted/added tests.

src/main/java/com/sk89q/worldedit/expression/Expression.java

@@ -78,4 +78,8 @@ public class Expression {
     public String toString() {
         return root.toString();
     }
+
+    public Invokable getVariable(String name) {
+        return variables.get(name);
+    }
 }

src/main/java/com/sk89q/worldedit/expression/lexer/Lexer.java

@@ -20,6 +20,7 @@
 package com.sk89q.worldedit.expression.lexer;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -43,15 +44,28 @@ public class Lexer {
     }
 
     private final DecisionTree operatorTree = new DecisionTree(null,
-            '-', new DecisionTree("-"),
+            '+', new DecisionTree("+",
-            '+', new DecisionTree("+"),
+                    '=', new DecisionTree("+="),
-            '*', new DecisionTree("*",
+                    '+', new DecisionTree("++")
-                    '*', new DecisionTree("^")
             ),
-            '/', new DecisionTree("/"),
+            '-', new DecisionTree("-",
-            '%', new DecisionTree("%"),
+                    '=', new DecisionTree("-="),
-            '^', new DecisionTree("^"),
+                    '-', new DecisionTree("--")
-            '=', new DecisionTree(null, // not implemented
+            ),
+            '*', new DecisionTree("*",
+                    '=', new DecisionTree("*="),
+                    '*', new DecisionTree("**")
+            ),
+            '/', new DecisionTree("/",
+                    '=', new DecisionTree("/=")
+            ),
+            '%', new DecisionTree("%",
+                    '=', new DecisionTree("%=")
+            ),
+            '^', new DecisionTree("^",
+                    '=', new DecisionTree("^=")
+            ),
+            '=', new DecisionTree("=",
                     '=', new DecisionTree("==")
             ),
             '!', new DecisionTree("!",
@@ -81,8 +95,13 @@ public class Lexer {
         characterTokens.add(',');
         characterTokens.add('(');
         characterTokens.add(')');
+        characterTokens.add('{');
+        characterTokens.add('}');
+        characterTokens.add(';');
     }
 
+    private static final Set<String> keywords = new HashSet<String>(Arrays.asList("if", "else"));
+
     private static final Pattern numberPattern = Pattern.compile("^([0-9]*(?:\\.[0-9]+)?(?:[eE][+-]?[0-9]+)?)");
     private static final Pattern identifierPattern = Pattern.compile("^([A-Za-z][0-9A-Za-z_]*)");
 
@@ -128,7 +147,12 @@ public class Lexer {
             if (identifierMatcher.lookingAt()) {
                 String identifierPart = identifierMatcher.group(1);
                 if (!identifierPart.isEmpty()) {
+                    if (keywords.contains(identifierPart)) {
+                        tokens.add(new KeywordToken(position, identifierPart));
+                    }
+                    else {
                         tokens.add(new IdentifierToken(position, identifierPart));
+                    }
 
                     position += identifierPart.length();
                     continue;

src/main/java/com/sk89q/worldedit/expression/lexer/tokens/KeywordToken.java

@@ -0,0 +1,39 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010, 2011 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.expression.lexer.tokens;
+
+public class KeywordToken extends Token {
+    public final String value;
+
+    public KeywordToken(int position, String value) {
+        super(position);
+        this.value = value;
+    }
+
+    @Override
+    public char id() {
+        return 'i';
+    }
+
+    @Override
+    public String toString() {
+        return "KeywordToken(" + value + ")";
+    }
+}

src/main/java/com/sk89q/worldedit/expression/parser/Parser.java

@@ -28,6 +28,7 @@ import java.util.List;
 import java.util.Map;
 
 import com.sk89q.worldedit.expression.Identifiable;
+import com.sk89q.worldedit.expression.lexer.tokens.CharacterToken;
 import com.sk89q.worldedit.expression.lexer.tokens.IdentifierToken;
 import com.sk89q.worldedit.expression.lexer.tokens.NumberToken;
 import com.sk89q.worldedit.expression.lexer.tokens.OperatorToken;
@@ -36,6 +37,7 @@ import com.sk89q.worldedit.expression.runtime.Constant;
 import com.sk89q.worldedit.expression.runtime.Functions;
 import com.sk89q.worldedit.expression.runtime.Invokable;
 import com.sk89q.worldedit.expression.runtime.Operators;
+import com.sk89q.worldedit.expression.runtime.Sequence;
 
 public class Parser {
     private final class NullToken extends Token {
@@ -66,7 +68,7 @@ public class Parser {
     }
 
     private Invokable parse() throws ParserException {
-        final Invokable ret = parseInternal();
+        final Invokable ret = parseInternal(true);
         if (position < tokens.size()) {
             final Token token = peek();
             throw new ParserException(token.getPosition(), "Extra token at the end of the input: " + token);
@@ -74,7 +76,7 @@ public class Parser {
         return ret;
     }
 
-    private final Invokable parseInternal() throws ParserException {
+    private final Invokable parseInternal(boolean isStatement) throws ParserException {
         LinkedList<Identifiable> halfProcessed = new LinkedList<Identifiable>();
 
         // process brackets, numbers, functions, variables and detect prefix operators
@@ -112,8 +114,15 @@ public class Parser {
                 expressionStart = false;
                 break;
 
+            case '{':
+                halfProcessed.add(parseBlock());
+                halfProcessed.add(new CharacterToken(-1, ';'));
+                expressionStart = false;
+                break;
+
             case ',':
             case ')':
+            case '}':
                 break loop;
 
             case 'o':
@@ -135,8 +144,57 @@ public class Parser {
             }
         }
 
+        if (isStatement) {
+            return processStatement(halfProcessed);
+        }
+        else {
             // process binary operators
-        return processBinaryOps(halfProcessed, binaryOpMaps.length - 1);
+            return processExpression(halfProcessed);
+        }
+    }
+
+    private Invokable processStatement(LinkedList<Identifiable> input) throws ParserException {
+        LinkedList<Identifiable> lhs = new LinkedList<Identifiable>();
+        LinkedList<Identifiable> rhs = new LinkedList<Identifiable>();
+        boolean semicolonFound = false;
+
+        for (Iterator<Identifiable> it = input.descendingIterator(); it.hasNext();) {
+            Identifiable identifiable = it.next();
+            if (semicolonFound) {
+                lhs.addFirst(identifiable);
+            }
+            else {
+                if (identifiable.id() == ';') {
+                    semicolonFound = true;
+                }
+                else {
+                    rhs.addFirst(identifiable);
+                }
+            }
+        }
+
+        if (lhs.isEmpty()) {
+            if (rhs.isEmpty()) {
+                return new Sequence(semicolonFound ? input.get(0).getPosition() : -1);
+            }
+
+            return processExpression(rhs);
+        }
+        else if (rhs.isEmpty()) {
+            return processStatement(lhs);
+        }
+        else {
+            assert(semicolonFound);
+
+            Invokable rhsInvokable = processExpression(rhs);
+            Invokable lhsInvokable = processStatement(lhs);
+
+            return new Sequence(position, lhsInvokable, rhsInvokable);
+        }
+    }
+
+    private Invokable processExpression(LinkedList<Identifiable> input) throws ParserException {
+        return processBinaryOps(input, binaryOpMaps.length - 1);
     }
 
     private static final Map<String, String>[] binaryOpMaps;
@@ -146,6 +204,7 @@ public class Parser {
         final Object[][][] binaryOps = {
                 {
                     { "^", "pow" },
+                    { "**", "pow" },
                 },
                 {
                     { "*", "mul" },
@@ -177,6 +236,15 @@ public class Parser {
                 {
                     { "||", "or" },
                 },
+                {
+                    { "=", "ass" },
+                    { "+=", "aadd" },
+                    { "-=", "asub" },
+                    { "*=", "amul" },
+                    { "/=", "adiv" },
+                    { "%=", "amod" },
+                    { "^=", "aexp" },
+                },
         };
 
         @SuppressWarnings("unchecked")
@@ -205,6 +273,8 @@ public class Parser {
         unaryOpMap.put("-", "neg");
         unaryOpMap.put("!", "not");
         unaryOpMap.put("~", "inv");
+        unaryOpMap.put("++", "inc");
+        unaryOpMap.put("--", "dec");
     }
 
     private Invokable processBinaryOps(LinkedList<Identifiable> input, int level) throws ParserException {
@@ -315,7 +385,7 @@ public class Parser {
             List<Invokable> args = new ArrayList<Invokable>();
 
             loop: while (true) {
-                args.add(parseInternal());
+                args.add(parseInternal(false));
 
                 final Token current = peek();
                 ++position;
@@ -345,7 +415,7 @@ public class Parser {
         }
         ++position;
 
-        final Invokable ret = parseInternal();
+        final Invokable ret = parseInternal(false);
 
         if (peek().id() != ')') {
             throw new ParserException(peek().getPosition(), "Unmatched opening bracket");
@@ -354,4 +424,20 @@ public class Parser {
 
         return ret;
     }
+
+    private final Invokable parseBlock() throws ParserException {
+        if (peek().id() != '{') {
+            throw new ParserException(peek().getPosition(), "Unexpected character in parseBlock");
+        }
+        ++position;
+
+        final Invokable ret = parseInternal(true);
+
+        if (peek().id() != '}') {
+            throw new ParserException(peek().getPosition(), "Unmatched opening brace");
+        }
+        ++position;
+
+        return ret;
+    }
 }

src/main/java/com/sk89q/worldedit/expression/runtime/Assignable.java

@@ -0,0 +1,28 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010, 2011 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.expression.runtime;
+
+public abstract class Assignable extends Invokable {
+    public Assignable(int position) {
+        super(position);
+    }
+
+    public abstract double assign(double value) throws EvaluationException;
+}

src/main/java/com/sk89q/worldedit/expression/runtime/Operators.java

@@ -21,10 +21,22 @@ package com.sk89q.worldedit.expression.runtime;
 
 public final class Operators {
     public static final Function getOperator(int position, String name, Invokable lhs, Invokable rhs) throws NoSuchMethodException {
+        if (lhs instanceof Assignable) {
+            try {
+                return new Function(position, Operators.class.getMethod(name, Assignable.class, Invokable.class), lhs, rhs);
+            }
+            catch (NoSuchMethodException e) {}
+        }
         return new Function(position, Operators.class.getMethod(name, Invokable.class, Invokable.class), lhs, rhs);
     }
 
     public static final Function getOperator(int position, String name, Invokable argument) throws NoSuchMethodException {
+        if (argument instanceof Assignable) {
+            try {
+                return new Function(position, Operators.class.getMethod(name, Assignable.class), argument);
+            }
+            catch (NoSuchMethodException e) {}
+        }
         return new Function(position, Operators.class.getMethod(name, Invokable.class), argument);
     }
 
@@ -116,6 +128,43 @@ public final class Operators {
     }
 
 
+    public static final double ass(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(rhs.invoke());
+    }
+
+    public static final double aadd(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(lhs.invoke() + rhs.invoke());
+    }
+
+    public static final double asub(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(lhs.invoke() - rhs.invoke());
+    }
+
+    public static final double amul(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(lhs.invoke() * rhs.invoke());
+    }
+
+    public static final double adiv(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(lhs.invoke() / rhs.invoke());
+    }
+
+    public static final double amod(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(lhs.invoke() % rhs.invoke());
+    }
+
+    public static final double aexp(Assignable lhs, Invokable rhs) throws EvaluationException {
+        return lhs.assign(Math.pow(lhs.invoke(), rhs.invoke()));
+    }
+
+    public static final double inc(Assignable x) throws EvaluationException {
+        return x.assign(x.invoke() + 1);
+    }
+
+    public static final double dec(Assignable x) throws EvaluationException {
+        return x.assign(x.invoke() - 1);
+    }
+
+
     // Usable AlmostEqual function, based on http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm
     private static boolean almostEqual2sComplement(double A, double B, long maxUlps) {
         // Make sure maxUlps is non-negative and small enough that the

src/main/java/com/sk89q/worldedit/expression/runtime/Sequence.java

@@ -0,0 +1,82 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010, 2011 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.expression.runtime;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Sequence extends Invokable {
+    private final Invokable[] sequence;
+
+    public Sequence(int position, Invokable... sequence) {
+        super(position);
+
+        this.sequence = sequence;
+    }
+
+    @Override
+    public char id() {
+        // TODO Auto-generated method stub
+        return 0;
+    }
+
+    @Override
+    public double invoke() throws EvaluationException {
+        double ret = 0;
+        for (Invokable invokable : sequence) {
+            ret = invokable.invoke();
+        }
+        return ret;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder("seq(");
+        boolean first = true;
+        for (Invokable invokable : sequence) {
+            if (!first) {
+                sb.append(", ");
+            }
+            sb.append(invokable);
+            first = false;
+        }
+
+        return sb.append(')').toString();
+    }
+
+    @Override
+    public Invokable optimize() throws EvaluationException {
+        List<Invokable> newSequence = new ArrayList<Invokable>();
+
+        for (Invokable invokable : sequence) {
+            invokable = invokable.optimize();
+            if (invokable instanceof Sequence) {
+                for (Invokable subInvokable : ((Sequence) invokable).sequence) {
+                    newSequence.add(subInvokable);
+                }
+            }
+            else {
+                newSequence.add(invokable);
+            }
+        }
+
+        return new Sequence(getPosition(), newSequence.toArray(new Invokable[newSequence.size()]));
+    }
+}

src/main/java/com/sk89q/worldedit/expression/runtime/Variable.java

@@ -19,7 +19,7 @@
 
 package com.sk89q.worldedit.expression.runtime;
 
-public final class Variable extends Invokable {
+public final class Variable extends Assignable {
     public double value;
 
     public Variable(double value) {
@@ -41,4 +41,9 @@ public final class Variable extends Invokable {
     public char id() {
         return 'v';
     }
+
+    @Override
+    public double assign(double value) {
+        return this.value = value;
+    }
 }

src/test/java/com/sk89q/worldedit/expression/ExpressionTest.java

@@ -31,7 +31,7 @@ public class ExpressionTest {
     public void testErrors() throws ExpressionException {
         // test lexer errors
         try {
-            Expression.compile("{");
+            Expression.compile("#");
             fail("Error expected");
         } catch (LexerException e) {
             assertEquals("Error position", 0, e.getPosition());
@@ -60,6 +60,15 @@ public class ExpressionTest {
         } catch (ParserException e) {}
     }
 
+    @Test
+    public void testAssign() throws ExpressionException {
+        Expression foo = Expression.compile("{a=x} b=y; c=z", "x", "y", "z", "a", "b", "c");
+        foo.evaluate(2, 3, 5);
+        assertEquals(2, foo.getVariable("a").invoke(), 0);
+        assertEquals(3, foo.getVariable("b").invoke(), 0);
+        assertEquals(5, foo.getVariable("c").invoke(), 0);
+    }
+
     private double simpleEval(String expression) throws Exception {
         return Expression.compile(expression).evaluate();
     }