PEGjs | Implement Variable in Parser-CodePudding

I am very beginner to PEGjs I need help to implement variable (identifier) declaration support to my parser.

My input code look like:

a=4;
print a

My PEGjs grammer:

start
=(line)*
line
=left:var"="right:integer";" {left=right;}
/ 
print middle:var {return middle;}
print
="print"
var
=(a-zA-z) 
Integer "integer"
= _ [0-9]  { return parseInt(text(), 10); }

Expected output: 4

Please help me. #ThanksInAdvance

CodePudding user response：

try this:

all
  = _ mn:multiPutN _ pn:printN _ 
  {
    return mn[pn];
  }

multiPutN
  = mp:putN  _ 
  {
    var r = {};
    mp.forEach(it => {
        r[it[0]]=it[1];
    });
    return r;
  }
  
putN
  = vn:varName _ "=" _ nn:n _ ";" { return [vn, nn]}

printN
  = print _ n:varName _ {return n;}
  
varName
  = [a-zA-Z]  {return text();}
  
print 
  ="print"

n "integer number"
  = _ [0-9]  { return parseInt(text(), 10); }
  
_ "whitespace or new line"
  = [ \t\n\r]*

so that code above also support multi variables but can only print one variable. I wrote the grammar based in your example so when assigning variable value you need to put ";" at the end but print var should not need with that