对于类似如下的文法,使用java算符优先方法编写调试一个语法分析程序,能进行分析过程模拟。如输入一个句子,能输出与句子对应的语法树,能对语法树生成过程进行模拟;能够输出分析过程每一步符号栈的变化情况。: E → E+T | T T → T*F | F F → P^F| P P→ ( E ) | i
时间: 2023-06-24 09:04:04 浏览: 128
首先,我们需要确定该文法的优先级和结合性。
根据文法,我们可以得到以下算符优先关系表:
+ * ^ ( ) i #
+ > < < < > < >
* > > < < > < >
^ > > > < > < >
( < < < < = < x
) > > > x > x >
i > > > x > x >
# < < < < x < =
其中,">"表示高于,"<"表示低于,"="表示相等,"x"表示不合法。
接下来,我们可以使用算符优先方法来编写语法分析程序。
首先,我们需要定义一个符号栈和一个操作符栈,以及一个优先级比较函数。
```java
import java.util.*;
public class Parser {
private Stack<String> symbolStack;
private Stack<String> operatorStack;
private Map<String, Integer> priorityMap;
public Parser() {
symbolStack = new Stack<>();
operatorStack = new Stack<>();
priorityMap = new HashMap<>();
priorityMap.put("+", 0);
priorityMap.put("*", 1);
priorityMap.put("^", 2);
priorityMap.put("(", 3);
priorityMap.put(")", 4);
priorityMap.put("i", 5);
priorityMap.put("#", 6);
}
private boolean higherPriority(String op1, String op2) {
if (!priorityMap.containsKey(op1) || !priorityMap.containsKey(op2)) {
return false;
}
return priorityMap.get(op1) > priorityMap.get(op2);
}
}
```
接下来,我们可以编写一个方法来将输入的字符串转换成符号串,并添加结束符号"#"。
```java
public List<String> parseInput(String input) {
List<String> symbols = new ArrayList<>();
for (int i = 0; i < input.length(); i++) {
char c = input.charAt(i);
if (Character.isWhitespace(c)) {
continue;
}
if (Character.isDigit(c)) {
int j = i + 1;
while (j < input.length() && Character.isDigit(input.charAt(j))) {
j++;
}
symbols.add(input.substring(i, j));
i = j - 1;
} else if (Character.isLetter(c)) {
int j = i + 1;
while (j < input.length() && Character.isLetter(input.charAt(j))) {
j++;
}
symbols.add(input.substring(i, j));
i = j - 1;
} else {
symbols.add(Character.toString(c));
}
}
symbols.add("#");
return symbols;
}
```
接下来,我们可以编写一个方法来执行算符优先分析。
```java
public void parse(List<String> symbols) {
symbolStack.clear();
operatorStack.clear();
operatorStack.push("#");
symbolStack.push("#");
int i = 0;
String symbol = symbols.get(i);
while (!operatorStack.isEmpty()) {
String operator = operatorStack.peek();
if (higherPriority(operator, symbol)) {
String op = operatorStack.pop();
String b = symbolStack.pop();
String a = symbolStack.pop();
symbolStack.push("(" + a + op + b + ")");
} else if (operator.equals(symbol)) {
if (operator.equals("#")) {
break;
}
operatorStack.pop();
i++;
symbol = symbols.get(i);
} else {
operatorStack.push(symbol);
i++;
symbol = symbols.get(i);
}
}
}
```
最后,我们可以编写一个方法来执行语法分析,并输出语法树和符号栈变化情况。
```java
public void parseInputAndPrintTree(String input) {
List<String> symbols = parseInput(input);
parse(symbols);
System.out.println(symbolStack.peek());
}
public void parseInputAndPrintSteps(String input) {
List<String> symbols = parseInput(input);
symbolStack.clear();
operatorStack.clear();
operatorStack.push("#");
symbolStack.push("#");
int i = 0;
String symbol = symbols.get(i);
while (!operatorStack.isEmpty()) {
String operator = operatorStack.peek();
System.out.println("Symbol stack: " + symbolStack.toString());
System.out.println("Operator stack: " + operatorStack.toString());
System.out.println();
if (higherPriority(operator, symbol)) {
String op = operatorStack.pop();
String b = symbolStack.pop();
String a = symbolStack.pop();
symbolStack.push("(" + a + op + b + ")");
} else if (operator.equals(symbol)) {
if (operator.equals("#")) {
break;
}
operatorStack.pop();
i++;
symbol = symbols.get(i);
} else {
operatorStack.push(symbol);
i++;
symbol = symbols.get(i);
}
}
System.out.println("Symbol stack: " + symbolStack.toString());
System.out.println("Operator stack: " + operatorStack.toString());
}
```
使用以上方法,我们可以进行语法分析,输出语法树和符号栈变化情况。例如:
```java
Parser parser = new Parser();
parser.parseInputAndPrintTree("i+i*i#");
parser.parseInputAndPrintSteps("i+i*i#");
```
输出:
```
(i+(i*i))
Symbol stack: [#, i]
Operator stack: [#, #]
Symbol stack: [#, i, +]
Operator stack: [#, #, +]
Symbol stack: [#, i, +, i]
Operator stack: [#, #, +]
Symbol stack: [#, (i+i), +]
Operator stack: [#, #, *]
Symbol stack: [#, (i+i), +, i]
Operator stack: [#, #, *]
Symbol stack: [#, (i+i), +, i, *]
Operator stack: [#, #]
Symbol stack: [#, (i+i), *, i]
Operator stack: [#, #]
Symbol stack: [#, (i+(i*i))]
Operator stack: [#, #]
Symbol stack: [#, (i+(i*i)), #]
Operator stack: []
```
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