Поддержка операций проверки равенства

src/com/annimon/everlastingsummer/Parser.java

@@ -412,7 +412,26 @@ public final class Parser {
     }
     
     private Expression expression() {
-        return additive();
+        return equality();
+    }
+    
+    private Expression equality() {
+        Expression expression = additive();
+        
+        if (lookMatch(1, TokenType.EQ)) {
+            if (match(TokenType.EQ)) {
+                // ==
+                match(TokenType.EQ);
+                return new BinaryExpression(Operator.EQUALS, expression, additive());
+            }
+            if (match(TokenType.EXCL)) {
+                // !=
+                match(TokenType.EQ);
+                return new BinaryExpression(Operator.NOTEQUALS, expression, additive());
+            }
+        }
+        
+        return expression;
     }
     
     private Expression additive() {

src/com/annimon/everlastingsummer/ast/BinaryExpression.java

@@ -6,7 +6,8 @@ package com.annimon.everlastingsummer.ast;
 public class BinaryExpression implements Expression {
     
     public static enum Operator {
-        ADD, SUBTRACT
+        ADD, SUBTRACT,
+        EQUALS, NOTEQUALS,
     }
 
     public final Operator operator;
@@ -25,6 +26,8 @@ public class BinaryExpression implements Expression {
         switch (operator) {
             case ADD: return leftVal + rightVal;
             case SUBTRACT: return leftVal - rightVal;
+            case EQUALS: return (leftVal == rightVal) ? 1 : 0;
+            case NOTEQUALS: return (leftVal != rightVal) ? 1 : 0;
             default:
                 throw new RuntimeException("Неизвестный оператор " + operator.name());
         }