自著——30天自制红孩儿解释器第14天执行IF和WHILE 语句（1）简单情况

2021-09-21 21:33:16 阅读：93 来源： 互联网

标签：arr 30 14 res 自著 else var result operator2

在第13天对IF进行了解析，今天开始对IF条件语句
执行，首先对BNF进行修改。

修改成
<if statement> :== <if statment section> ( null | <else statement section>
| <else if statement section> | <else if statement section> <else statement section>   )
<if statment section>       :== IF <if statement body>
<else if statement section> :== else if <if statement body> <else if statement section>
<else statement section>    :== ELSE <else body>

以上的修改，为第14.1版本的程序。

第14天第二版本程序
a=1; if(a>1) {b=2;}

第14天第三版本程序
a=1;while (a<10) {a=a+1;}

增加WHILE 循环语句的BNF定义。
<while statment> :== WHILE <while statement body>
<while statement body> :== ( <logic expression> ) <while body>
<while body> :== { <statement list> }

<HTML>
<HEAD>
<TITLE> 30天自制解释器 14.1 </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<script src='get_token_general.js' ></script>
<script src='execute_lib.js' ></script>
<script src='symbol_table_operation.js' ></script>
</HEAD>
<BODY>
<p></p>
<p></p>
<p> aget_token_general=5;
b=a+1;
a
</p>
<p> </p>
<p>解析IF 语句，本版本与13.4 功能相同。程序重构。</p>
<p>if (a>1) {b=2;} else if (a==1) {c=2;}</p>
<textarea id='txt1' rows="20" cols="80"></textarea>
<input type='button' value='翻译成lisp程序' οnclick='eval()'>第十四天第一版</input>
<input type='button' value='执行' οnclick='execute()'>execute</input>
<textarea id='txt2' rows="20" cols="80"></textarea>
<p>error show area:</p>
<textarea id='txt3' rows="20" cols="80"></textarea>
<script>
function eval()
{
var str=document.getElementById("txt1").innerText;
var result=0;
var token_array=[];
var result_str="";
token_array=get_token_general({"lineno":1,"linelength":str.length,"str":str},token_array);

// result=parse_sim_exp(token_array,0,0);
//   result=parse_relation_exp(token_array,0,0);
     //   result=parse_logic_exp(token_array,0,0);
   result= parse_compound_statement(token_array,0,0);
   // result=test_symboltable_operation(token_array);
// if (hasError(result.res)==0)
      // result=execute_exp(token_array);
    // result_str=sysmbol_table_arrtostring(result);
document.getElementById("txt2").innerText=result.res;//result_str; //
}

fujction parse_compound_statement(arr,i,level)
{
var result="";
var resultstr="";
while(i<arr.length-1&&arr[i].value!='}')
    {
       if(arr[i].value==';')
         {i+=1;}
       if (isVariable(arr[i])==1) {
              result=parse_assign_statement(arr,i,level);
                i=result.i;
                resultstr=resultstr+" "+result.res;
           }
         else if (arr[i].value=='if')
          {
             result=parse_if_statement(arr,i,level+1);
               i=result.i;
               resultstr=resultstr+" "+result.res;
          }

       if(i<arr.length-1&&arr[i+1].value==';')
         {i+=1;}
       else
          {break;}
   }
     return {"res":resultstr,"i":i-1};
}

   return   {"res":result,"i":i};
}
function parse_else_if_statement_section(arr,i,level)
{
       var operator2={};
        var operator3={};
        var result="";
       if (i<arr.length-2&&arr[i].value=='else' && (arr[i+1].value=='if'))
                     {
                       operator2=parse_if_statement_body(arr,i+2,level);
                      if( hasError(operator2.res)==-1)
                        {
                            result=operator2.res;
                            i=operator2.i;
                            operator3=parse_else_if_statement_section(arr,i+1,level);
                             if( hasError(operator3.res)==-1)
                             {i=operator3.i;
                               result= operator2.res+" "+operator3.res;
                         // result=make_lisp_program_action("if",operator2.res,operator3.res);
                              }
                             else if(hasError(operator3.res)>=0)
                               {result=operator3.res;
                               }
                         }
                     else if(hasError(operator2.res)>=0)
                         {result=operator2.res;
                         }
                   }
         else {i=i-1;}
    return   {"res":result,"i":i};
}

   return   {"res":result,"i":i};
}
function parse_else_body(arr,i,level)
{
     var result="";
   var operator2={};
   var operator3={};
   if (arr[i].value=='{')
          {
            i=i+1;
           operator2=parse_compound_statement(arr,i,level);
           if( hasError(operator2.res)==-1)
                {
                  //result=make_lisp_program_action(arr[i+1].value,result,operator2.res);
                  i=operator2.i+1;
                  if(i<arr.length&&arr[i].value=='}'){
                  result= operator2.res;
                  }
                  else {
                      result='[error]: is not a block }: at '+arr[i].startindex+" value: "+arr[i].value;
                  }
                }
             else if(hasError(operator2.res)>=0)
                {result=operator2.res;
                }
          }
    else {
        result='[error]: is not a block {: at '+arr[i].startindex+" value: "+arr[i].value;
   }

return {"res":result,"i":i};
}

function parse_assign_statement(arr,i,level)
{
      var operator1={};
   var operator2={};
   var result="";

        operator1= parse_variable(arr,i,level);
       if(hasError(operator1.res)>=0)
              {
                 return {"res":operator1.res,"i":i};
              }
              else {result =operator1.res;
              i=operator1.i;
              }

   if ( i<arr.length-2 &&(arr[i+1].value=='=') )
     {
       operator2= parse_logic_exp(arr,i+2,level);
       if( hasError(operator2.res)==-1)
           {
         result=make_lisp_program_action(arr[i+1].value,result,operator2.res);
       //result=execute_binary_relation_operator_action(arr[i+1].value,result,operator2.res);
           i=operator2.i;
           }
       else if(hasError(operator2.res)>=0)
              {result=operator2.res;
           // break;
              }

   }
    return {"res":result,"i":i};
}

function parse_variable(arr,i,level)
{
var result=0;
// var resultObj={};

   if(isVariable(arr[i])==1)
     {result=arr[i].value;}
   else
       {result='[error]: is not a vairable: at '+arr[i].startindex+" value: "+arr[i].value;}
    return {"res":result,"i":i};
}
function parse_logic_exp(arr,i,level)
{
   var operator1={};
   var operator2={};
   var result="";

        operator1= parse_relation_exp(arr,i,level);
       if(hasError(operator1.res)>=0)
              {
                 return {"res":operator1.res,"i":i};
              }
              else {result =operator1.res;
              i=operator1.i;
              }

   while( i<arr.length-2 &&(arr[i+1].value=='&&'||arr[i+1].value=='||' || arr[i+1].value=='^^') )
     {
       operator2= parse_relation_exp(arr,i+2,level);
       if( hasError(operator2.res)==-1)
           {
       //result=execute_binary_logic_operator_action(arr[i+1].value,result,operator2.res);
           result=make_lisp_program_action(arr[i+1].value,result,operator2.res);
           i=operator2.i;
           }
       else if(hasError(operator2.res)>=0)
              {result=operator2.res;
               break;
              }

   }
    return {"res":result,"i":i};
}

function parse_relation_exp(arr,i,level)
{
       var operator1={};
   var operator2={};
   var result="";

        operator1= parse_sim_exp(arr,i,level);
       if(hasError(operator1.res)>=0)
              {
                 return {"res":operator1.res,"i":i};
              }
              else {result =operator1.res;
              i=operator1.i;
              }

   if ( i<arr.length-2 &&(arr[i+1].value=='>'||arr[i+1].value=='<'||arr[i+1].value=='>='||arr[i+1].value=='<='||arr[i+1].value=='=='||arr[i+1].value=='<>') )
     {
       operator2= parse_sim_exp(arr,i+2,level);
       if( hasError(operator2.res)==-1)
           {
       //result=execute_binary_relation_operator_action(arr[i+1].value,result,operator2.res);
          result=make_lisp_program_action(arr[i+1].value,result,operator2.res);
           i=operator2.i;
           }
       else if(hasError(operator2.res)>=0)
              {result=operator2.res;
           // break;
              }

   }
    return {"res":result,"i":i};
}

function parse_sim_exp(arr,i,level)
{
   var operator1={};
   var operator2={};
   var result="";

        operator1= parse_term(arr,i,level);
       if(hasError(operator1.res)>=0)
              {
                 return {"res":operator1.res,"i":i};
              }
              else {result =operator1.res;
              i=operator1.i;
              }

   while( i<arr.length-2 &&(arr[i+1].value=='+'||arr[i+1].value=='-') )
     {
       operator2= parse_term(arr,i+2,level);
       if( hasError(operator2.res)==-1)
           {
   //   result=execute_binary_calc_operator_action(arr[i+1].value,result,operator2.res);
   result=make_lisp_program_action(arr[i+1].value,result,operator2.res);
           i=operator2.i;
           }
       else if(hasError(operator2.res)>=0)
              {result=operator2.res;
               break;
              }

   }
    return {"res":result,"i":i};
}

   while( i<arr.length-2 &&(arr[i+1].value=='*'||arr[i+1].value=='/') )
     {
       operator2= parse_factor(arr,i+2,level);

       if( hasError(operator2.res)==-1)
           {
          // result=execute_binary_calc_operator_action(arr[i+1].value,result,operator2.res);
           result=make_lisp_program_action(arr[i+1].value,result,operator2.res);
            i=operator2.i;
           }
       else if(hasError(operator2.res)>=0)
              {result=operator2.res;
               break;
              }

}

return {"res":result,"i":i};
}

function parse_factor(arr,i,level)
{
var result=0;
var resultObj={};

   if(isNum(arr[i].value)==1)
     {result=arr[i].value;}
    else if (arr[i].type==7)
      {
         if (arr[i].value=='(')
       {
                 resultObj=parse_sim_exp(arr,i+1,level+1);
               result=resultObj.res;
               i=resultObj.i;
       }

          if (i<arr.length-1&& arr[i+1].value==')')
          {
                 i=i+1;
          }
          else if (i==arr.length-1 && arr[i]!=')')
              {
                   result='[error]: should be ) : at '+arr[i].startindex+" but value: "+arr[i].value;
              }
          else
          {
              result='[error]: should be ) : at '+arr[i].startindex+" but value: "+arr[i].value;
          }
      }
   else if (isVariable(arr[i])==1)
        {
           result= arr[i].value;
       }
   else
       {result='[error]: is not number: at '+arr[i].startindex+" value: "+arr[i].value;}
    return {"res":result,"i":i};
}

function hasError(str)
{
if(isNum(str)==1)
return -1;
else
return str.indexOf("error");
}

function make_lisp_program_action(operand,operator1,operator2)
{
return "("+ operand + " "+operator1+" "+operator2+")";
}

</script>
</BODY>
</HTML>

标签：arr,30,14,res,自著,else,var,result,operator2
来源： https://blog.csdn.net/gggwfn1982/article/details/120405685

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自著——30天自制红孩儿解释器 第14天 执行IF和WHILE 语句（1）简单情况

自著——30天自制红孩儿解释器第14天执行IF和WHILE 语句（1）简单情况