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--- jail:interpreter [2024/07/19 00:42]
127.0.0.1 Externe Bearbeitung
+++ jail:interpreter [2025/07/10 11:55] (aktuell)
jango
@@ Zeile 1: / Zeile 1: @@
+Siehe auch [[jail:lexer]], [[jail:parser]]
+[[https://rpallas.xyz/math-parser/]]
+====== Interpreter ======
+The parser has finally generated a rooted, structured AST tree.
+<code>
+Token('CODE_BLOCK', 'CODE_BLOCK')
+  Token('ASSIGN', '=')
+    Token('VARIABLE', 'a')
+    Token('INTEGER', '1')
+  Token('ASSIGN', '=')
+    Token('VARIABLE', 'b')
+    Token('INTEGER', '2')
+</code>
+The interpreter traverses the tree and visits each node. If its for example an ASSIGN token, there has to be 2 children – the variable name and the value which should be stored. This is the most important part. It is where variables get created and managed.
+<code c++>
+class Interpreter {
+	private:
+		Parser parser;
+	public:
+		Interpreter(Parser _parser) {
+			parser = _parser;
+		}
+		~Interpreter() {};
+		Token interpret() {
+			ASTNode tree = parser.parse();
+			return visit(tree);
+		}
+		Token visit(ASTNode node) {
+			if(node._token()._type() == EMPTY) {
+				return Token(INTEGER, "0");
+			}
+			else if(node._token()._type() == CODE_BLOCK) {
+				Token token;
+				for(auto it = node.child.begin(); it != node.child.end(); it++) {
+					token = visit(**it);
+				}
+				return token;
+			}
+			else if(node._token()._type() == INTEGER) {
+				return node._token();
+			}
+			else if (node._token()._type() == ASSIGN) {
+				Token token = visit(*node.child[1]);
+				if (token._type() == INTEGER) {
+					int i = 0;
+					try {
+						i = stoi(token._value());
+					} catch(...) {
+						return Token(INTEGER, "1"); // indicating error
+					}
+					printf("Assigning Integer %d\n", i );
+				}
+			}
+			return Token(INTEGER, "0");
+		}
+};
+</code>

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