Урок 3. Оператор присвоения, переменные

src/com/annimon/ownlang/Main.java

@@ -1,9 +1,10 @@
 package com.annimon.ownlang;
 
+import com.annimon.ownlang.lib.Variables;
 import com.annimon.ownlang.parser.Lexer;
 import com.annimon.ownlang.parser.Parser;
 import com.annimon.ownlang.parser.Token;
-import com.annimon.ownlang.parser.ast.Expression;
+import com.annimon.ownlang.parser.ast.Statement;
 import java.util.List;
 
 /**
@@ -12,17 +13,22 @@ import java.util.List;
 public final class Main {
 
     public static void main(String[] args) {
-        final String input1 = "2 + 2";
+        final String input1 = "word = 2 + 2\nword2 = PI + word";
 //        final String input2 = "(GOLDEN_RATIO + 2) * #f";
         final String input2 = "GOLDEN_RATIO";
-        final List<Token> tokens = new Lexer(input2).tokenize();
+        final List<Token> tokens = new Lexer(input1).tokenize();
         for (Token token : tokens) {
             System.out.println(token);
         }
         
-        final List<Expression> expressions = new Parser(tokens).parse();
-        for (Expression expr : expressions) {
-            System.out.println(expr + " = " + expr.eval());
-        }
+        final List<Statement> statements = new Parser(tokens).parse();
+        for (Statement statement : statements) {
+            System.out.println(statement);
+        }
+        for (Statement statement : statements) {
+            statement.execute();
+        }
+        System.out.printf("%s = %f\n", "word", Variables.get("word"));
+        System.out.printf("%s = %f\n", "word2", Variables.get("word2"));
     }
 }

src/com/annimon/ownlang/lib/Constants.java

@@ -1,30 +0,0 @@
-package com.annimon.ownlang.lib;
-
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- *
- * @author aNNiMON
- */
-public final class Constants {
-
-    private static final Map<String, Double> constants;
-    
-    static {
-        constants = new HashMap<>();
-        constants.put("PI", Math.PI);
-        constants.put("ПИ", Math.PI);
-        constants.put("E", Math.E);
-        constants.put("GOLDEN_RATIO", 1.618);
-    }
-    
-    public static boolean isExists(String key) {
-        return constants.containsKey(key);
-    }
-    
-    public static double get(String key) {
-        if (!isExists(key)) return 0;
-        return constants.get(key);
-    }
-}

src/com/annimon/ownlang/lib/Variables.java

@@ -0,0 +1,34 @@
+package com.annimon.ownlang.lib;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public final class Variables {
+
+    private static final Map<String, Double> variables;
+    
+    static {
+        variables = new HashMap<>();
+        variables.put("PI", Math.PI);
+        variables.put("ПИ", Math.PI);
+        variables.put("E", Math.E);
+        variables.put("GOLDEN_RATIO", 1.618);
+    }
+    
+    public static boolean isExists(String key) {
+        return variables.containsKey(key);
+    }
+    
+    public static double get(String key) {
+        if (!isExists(key)) return 0;
+        return variables.get(key);
+    }
+    
+    public static void set(String key, double value) {
+        variables.put(key, value);
+    }
+}

src/com/annimon/ownlang/parser/Lexer.java

@@ -9,11 +9,12 @@ import java.util.List;
  */
 public final class Lexer {
     
-    private static final String OPERATOR_CHARS = "+-*/()";
+    private static final String OPERATOR_CHARS = "+-*/()=";
     private static final TokenType[] OPERATOR_TOKENS = {
         TokenType.PLUS, TokenType.MINUS,
         TokenType.STAR, TokenType.SLASH,
         TokenType.LPAREN, TokenType.RPAREN,
+        TokenType.EQ
     };
 
     private final String input;

src/com/annimon/ownlang/parser/Parser.java

@@ -1,9 +1,11 @@
 package com.annimon.ownlang.parser;
 
+import com.annimon.ownlang.parser.ast.AssignmentStatement;
 import com.annimon.ownlang.parser.ast.BinaryExpression;
-import com.annimon.ownlang.parser.ast.ConstantExpression;
+import com.annimon.ownlang.parser.ast.VariabletExpression;
 import com.annimon.ownlang.parser.ast.Expression;
 import com.annimon.ownlang.parser.ast.NumberExpression;
+import com.annimon.ownlang.parser.ast.Statement;
 import com.annimon.ownlang.parser.ast.UnaryExpression;
 import java.util.ArrayList;
 import java.util.List;
@@ -26,14 +28,31 @@ public final class Parser {
         size = tokens.size();
     }
     
-    public List<Expression> parse() {
-        final List<Expression> result = new ArrayList<>();
+    public List<Statement> parse() {
+        final List<Statement> result = new ArrayList<>();
         while (!match(TokenType.EOF)) {
-            result.add(expression());
+            result.add(statement());
         }
         return result;
     }
     
+    private Statement statement() {
+        return assignmentStatement();
+    }
+    
+    private Statement assignmentStatement() {
+        // WORD EQ
+        final Token current = get(0);
+        if (match(TokenType.WORD) && get(0).getType() == TokenType.EQ) {
+            final String variable = current.getText();
+            consume(TokenType.EQ);
+            return new AssignmentStatement(variable, expression());
+        }
+        throw new RuntimeException("Unknown statement");
+    }
+    
+    
+    
     private Expression expression() {
         return additive();
     }
@@ -94,7 +113,7 @@ public final class Parser {
             return new NumberExpression(Long.parseLong(current.getText(), 16));
         }
         if (match(TokenType.WORD)) {
-            return new ConstantExpression(current.getText());
+            return new VariabletExpression(current.getText());
         }
         if (match(TokenType.LPAREN)) {
             Expression result = expression();
@@ -104,6 +123,13 @@ public final class Parser {
         throw new RuntimeException("Unknown expression");
     }
     
+    private Token consume(TokenType type) {
+        final Token current = get(0);
+        if (type != current.getType()) throw new RuntimeException("Token " + current + " doesn't match " + type);
+        pos++;
+        return current;
+    }
+    
     private boolean match(TokenType type) {
         final Token current = get(0);
         if (type != current.getType()) return false;

src/com/annimon/ownlang/parser/TokenType.java

@@ -14,6 +14,7 @@ public enum TokenType {
     MINUS,
     STAR,
     SLASH,
+    EQ,
     
     LPAREN, // (
     RPAREN, // )

src/com/annimon/ownlang/parser/ast/AssignmentStatement.java

@@ -0,0 +1,29 @@
+package com.annimon.ownlang.parser.ast;
+
+import com.annimon.ownlang.lib.Variables;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public final class AssignmentStatement implements Statement {
+
+    private final String variable;
+    private final Expression expression;
+
+    public AssignmentStatement(String variable, Expression expression) {
+        this.variable = variable;
+        this.expression = expression;
+    }
+    
+    @Override
+    public void execute() {
+        final double result = expression.eval();
+        Variables.set(variable, result);
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s = %s", variable, expression);
+    }
+}

src/com/annimon/ownlang/parser/ast/Statement.java

@@ -0,0 +1,10 @@
+package com.annimon.ownlang.parser.ast;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public interface Statement {
+    
+    void execute();
+}

src/com/annimon/ownlang/parser/ast/VariabletExpression.java

@@ -1,23 +1,23 @@
 package com.annimon.ownlang.parser.ast;
 
-import com.annimon.ownlang.lib.Constants;
+import com.annimon.ownlang.lib.Variables;
 
 /**
  *
  * @author aNNiMON
  */
-public final class ConstantExpression implements Expression {
+public final class VariabletExpression implements Expression {
     
     private final String name;
     
-    public ConstantExpression(String name) {
+    public VariabletExpression(String name) {
         this.name = name;
     }
 
     @Override
     public double eval() {
-        if (!Constants.isExists(name)) throw new RuntimeException("Constant does not exists");
-        return Constants.get(name);
+        if (!Variables.isExists(name)) throw new RuntimeException("Constant does not exists");
+        return Variables.get(name);
     }
 
     @Override