1. 语法分析转换
源码
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class Demo{
function void main() {
var Array a;
var int length;
var int i;
while (i < length) {
let a[i] = Keyboard.readInt("ENTER THE NEXT NUMBER: ");
let i = i + 1;
}
}
}
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<class>
<keyword> class </keyword>
<identifier> Demo </identifier>
<symbol> { </symbol>
<subroutineDec> <!-- // 描述函数 方法 构造函数 -->
<keyword> function </keyword>
<keyword> void </keyword>
<identifier> main </identifier>
<symbol> ( </symbol>
<parameterList> </parameterList>
<symbol> ) </symbol>
<subroutineBody> <!-- 描述函数 方法 构造函数 体 -->
<symbol> { </symbol>
<varDec> <!-- 构造表达式 -->
<keyword> var </keyword>
<identifier> Array </identifier>
<identifier> a </identifier>
<symbol> ; </symbol>
</varDec>
<varDec>
<keyword> var </keyword>
<keyword> int </keyword>
<identifier> length </identifier>
<symbol> ; </symbol>
</varDec>
<varDec>
<keyword> var </keyword>
<keyword> int </keyword>
<identifier> i </identifier>
<symbol> ; </symbol>
</varDec>
<statements> <!-- 语句 -->
<whileStatement> <!-- 循环语句 -->
<keyword> while </keyword>
<symbol> ( </symbol>
<expression>
<term> <!-- 简单来说，就是 term会有歧义 我不知道 i 是一个变量 还是数组 还是子程序调用 所以我要提前查看下一个字元 -->
<identifier> i </identifier>
</term>
<symbol> < </symbol>
<term>
<identifier> length </identifier>
</term>
</expression>
<symbol> ) </symbol>
<symbol> { </symbol>
<statements>
<letStatement>
<keyword> let </keyword>
<identifier> a </identifier>
<symbol> [ </symbol>
<expression>
<term>
<identifier> i </identifier>
</term>
</expression>
<symbol> ] </symbol>
<symbol> = </symbol>
<expression>
<term>
<identifier> Keyboard </identifier>
<symbol> . </symbol>
<identifier> readInt </identifier>
<symbol> ( </symbol>
<expressionList>
<expression>
<term>
<stringConstant> ENTER THE NEXT NUMBER: </stringConstant>
</term>
</expression>
</expressionList>
<symbol> ) </symbol>
</term>
</expression>
<symbol> ; </symbol>
</letStatement>
<letStatement>
<keyword> let </keyword>
<identifier> i </identifier>
<symbol> = </symbol>
<expression>
<term>
<identifier> i </identifier>
</term>
<symbol> + </symbol>
<term>
<integerConstant> 1 </integerConstant>
</term>
</expression>
<symbol> ; </symbol>
</letStatement>
</statements>
<symbol> } </symbol>
</whileStatement>
</statements>
<symbol> } </symbol>
</subroutineBody>
</subroutineDec>
<symbol> } </symbol>
</class>
2. 语法分析
源码
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class Demo{
function void main() {
var SquareGame game;
return;
}
}
翻译
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<class>
<keyword> class </keyword>
<identifier> Demo </identifier>
<symbol> { </symbol>
<subroutineDec>
<keyword> function </keyword>
<keyword> void </keyword>
<identifier> main </identifier>
<symbol> ( </symbol>
<parameterList> </parameterList>
<symbol> ) </symbol>
<subroutineBody>
<symbol> { </symbol>
<varDec>
<keyword> var </keyword>
<identifier> SquareGame </identifier>
<identifier> game </identifier>
<symbol> ; </symbol>
</varDec>
<statements>
<returnStatement>
<keyword> return </keyword>
<symbol> ; </symbol>
</returnStatement>
</statements>
<symbol> } </symbol>
</subroutineBody>
</subroutineDec>
<symbol> } </symbol>
</class>