用JAVA语言编写一门语言的语义分析器,并准备2~3个测试用例,测试并解释程序的运行结果
时间: 2024-05-09 10:16:01 浏览: 9
好的,我可以为您介绍一下如何编写一门语言的语义分析器,并提供一些测试用例。
编写一门语言的语义分析器通常需要以下步骤:
1. 设计语言的语法规则:定义关键字、操作符、数据类型、变量等,并将它们组合成语句和表达式。
2. 实现词法分析器:将输入的源代码分解成一个个单独的词语,例如关键字、操作符、变量名等。
3. 实现语法分析器:将词法分析器生成的词汇流转换成语法树,检查它们是否符合语言的语法规则。
4. 实现语义分析器:对语法树进行遍历,检查语法正确性和语义正确性。例如,检查变量是否已声明、类型是否匹配等。
下面是一个简单的Java语言的语义分析器实现示例:
```java
public class SemanticAnalyzer {
private Map<String, String> symbolTable = new HashMap<>();
private String currentType;
public void analyzeSyntaxTree(SyntaxTree tree) {
for (SyntaxTree node : tree.getChildren()) {
switch (node.getType()) {
case "variable_declaration":
currentType = node.getChild(0).getValue();
for (SyntaxTree varNode : node.getChild(1).getChildren()) {
String varName = varNode.getValue();
if (symbolTable.containsKey(varName)) {
throw new RuntimeException("Variable " + varName + " has already been declared");
}
symbolTable.put(varName, currentType);
}
break;
case "assignment_statement":
String varName = node.getChild(0).getValue();
if (!symbolTable.containsKey(varName)) {
throw new RuntimeException("Variable " + varName + " has not been declared");
}
String expressionType = analyzeExpression(node.getChild(1));
if (!expressionType.equals(symbolTable.get(varName))) {
throw new RuntimeException("Type mismatch for variable " + varName);
}
break;
default:
for (SyntaxTree childNode : node.getChildren()) {
analyzeSyntaxTree(childNode);
}
break;
}
}
}
private String analyzeExpression(SyntaxTree node) {
if (node.getType().equals("identifier")) {
String varName = node.getValue();
if (!symbolTable.containsKey(varName)) {
throw new RuntimeException("Variable " + varName + " has not been declared");
}
return symbolTable.get(varName);
} else if (node.getType().equals("literal")) {
return node.getValue();
} else {
String leftType = analyzeExpression(node.getChild(0));
String rightType = analyzeExpression(node.getChild(1));
if (!leftType.equals(rightType)) {
throw new RuntimeException("Type mismatch in expression");
}
return leftType;
}
}
}
```
上面的代码中,我们使用了一个符号表(symbolTable)来存储变量和类型之间的映射关系。在分析变量声明和赋值语句时,我们会更新符号表,并进行一些检查,例如检查变量是否已经声明、是否类型匹配等。
下面是几个测试用例:
```java
public class SemanticAnalyzerTest {
@Test
public void testVariableDeclaration() {
String sourceCode = "int x, y, z;";
SyntaxTree syntaxTree = parseSourceCode(sourceCode);
SemanticAnalyzer analyzer = new SemanticAnalyzer();
analyzer.analyzeSyntaxTree(syntaxTree);
assertEquals("int", analyzer.getSymbolTable().get("x"));
assertEquals("int", analyzer.getSymbolTable().get("y"));
assertEquals("int", analyzer.getSymbolTable().get("z"));
}
@Test
public void testAssignmentStatement() {
String sourceCode = "int x = 1;";
SyntaxTree syntaxTree = parseSourceCode(sourceCode);
SemanticAnalyzer analyzer = new SemanticAnalyzer();
analyzer.analyzeSyntaxTree(syntaxTree);
assertEquals("int", analyzer.getSymbolTable().get("x"));
sourceCode = "x = 2.0;";
syntaxTree = parseSourceCode(sourceCode);
assertThrows(RuntimeException.class, () -> analyzer.analyzeSyntaxTree(syntaxTree));
}
@Test
public void testTypeMismatch() {
String sourceCode = "int x = 1; double y = 2.0;";
SyntaxTree syntaxTree = parseSourceCode(sourceCode);
SemanticAnalyzer analyzer = new SemanticAnalyzer();
analyzer.analyzeSyntaxTree(syntaxTree);
sourceCode = "x = y;";
syntaxTree = parseSourceCode(sourceCode);
assertThrows(RuntimeException.class, () -> analyzer.analyzeSyntaxTree(syntaxTree));
}
}
```
第一个测试用例测试变量声明,第二个测试用例测试赋值语句,第三个测试用例测试类型不匹配的情况。
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