Урок 2. Вещественные числа, константы

src/com/annimon/ownlang/Main.java

@@ -13,7 +13,8 @@ public final class Main {
 
     public static void main(String[] args) {
         final String input1 = "2 + 2";
-        final String input2 = "(2 + 2) * #f";
+//        final String input2 = "(GOLDEN_RATIO + 2) * #f";
+        final String input2 = "GOLDEN_RATIO";
         final List<Token> tokens = new Lexer(input2).tokenize();
         for (Token token : tokens) {
             System.out.println(token);

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

@@ -0,0 +1,30 @@
+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/parser/Lexer.java

@@ -34,6 +34,7 @@ public final class Lexer {
         while (pos < length) {
             final char current = peek(0);
             if (Character.isDigit(current)) tokenizeNumber();
+            else if (Character.isLetter(current)) tokenizeWord();
             else if (current == '#') {
                 next();
                 tokenizeHexNumber();
@@ -51,7 +52,12 @@ public final class Lexer {
     private void tokenizeNumber() {
         final StringBuilder buffer = new StringBuilder();
         char current = peek(0);
-        while (Character.isDigit(current)) {
+        while (true) {
+            if (current == '.') {
+                if (buffer.indexOf(".") != -1) throw new RuntimeException("Invalid float number");
+            } else if (!Character.isDigit(current)) {
+                break;
+            }
             buffer.append(current);
             current = next();
         }
@@ -78,6 +84,19 @@ public final class Lexer {
         next();
     }
     
+    private void tokenizeWord() {
+        final StringBuilder buffer = new StringBuilder();
+        char current = peek(0);
+        while (true) {
+            if (!Character.isLetterOrDigit(current) && (current != '_')  && (current != '$')) {
+                break;
+            }
+            buffer.append(current);
+            current = next();
+        }
+        addToken(TokenType.WORD, buffer.toString());
+    }
+    
     private char next() {
         pos++;
         return peek(0);

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

@@ -1,6 +1,7 @@
 package com.annimon.ownlang.parser;
 
 import com.annimon.ownlang.parser.ast.BinaryExpression;
+import com.annimon.ownlang.parser.ast.ConstantExpression;
 import com.annimon.ownlang.parser.ast.Expression;
 import com.annimon.ownlang.parser.ast.NumberExpression;
 import com.annimon.ownlang.parser.ast.UnaryExpression;
@@ -92,6 +93,9 @@ public final class Parser {
         if (match(TokenType.HEX_NUMBER)) {
             return new NumberExpression(Long.parseLong(current.getText(), 16));
         }
+        if (match(TokenType.WORD)) {
+            return new ConstantExpression(current.getText());
+        }
         if (match(TokenType.LPAREN)) {
             Expression result = expression();
             match(TokenType.RPAREN);

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

@@ -8,6 +8,7 @@ public enum TokenType {
 
     NUMBER,
     HEX_NUMBER,
+    WORD,
     
     PLUS,
     MINUS,

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

@@ -29,6 +29,6 @@ public final class BinaryExpression implements Expression {
 
     @Override
     public String toString() {
-        return String.format("%s %c %s", expr1, operation, expr2);
+        return String.format("[%s %c %s]", expr1, operation, expr2);
     }
 }

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

@@ -0,0 +1,28 @@
+package com.annimon.ownlang.parser.ast;
+
+import com.annimon.ownlang.lib.Constants;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public final class ConstantExpression implements Expression {
+    
+    private final String name;
+    
+    public ConstantExpression(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public double eval() {
+        if (!Constants.isExists(name)) throw new RuntimeException("Constant does not exists");
+        return Constants.get(name);
+    }
+
+    @Override
+    public String toString() {
+//        return String.format("%s [%f]", name, Constants.get(name));
+        return String.format("%s", name);
+    }
+}