function PEG

start
 = calculation

calculation
 = p:program {
return p;
return eval(p);
}

program
 = __? f:functions __? { return f; }

functions
 = functionMain
 / n:functionNormal ___ o:functions { return o; }

functionNormal
 = i:id _? f:funcNotId { return [i,f]; }

functionMain
 = i:"main" _? f:funcNotId { return f; }

funcNotId
 = a:funcArgs __? b:funcBody {
function flatten(arr) {
  return arr.reduce(function (flat, toFlatten) {
    return flat.concat(Array.isArray(toFlatten) ? flatten(toFlatten) : toFlatten);
  }, []);
}

b = flatten(b);
h = {};
for (i = 0; i < b.length; i+=2){
 h[b[i]] = b[i+1];
}

output = h["return"];

output_tokens = output.match(/[0-9]+|[a-zA-Z]+|[-+*/]/g);

function substitute(ary){
 for (i = 0; i < ary.length; i++){
  toks = ary[i].match(/[0-9]+|[a-zA-Z]+|[-+*/()]/g);
  for (j = 0; j < toks.length; j++){
   if (h[toks[j]] != null) {
    toks[j] = "("+h[toks[j]]+")";
   }
  }
  ary[i] = toks.join("");
 }
return ary
}

for(l = 0; l < b.length / 2 - 1; l++){
 output_tokens = substitute(output_tokens);
}

return output_tokens.join("");
}

funcArgs
 = "(" _? a:args { return a; }
 / "(" _? ")" { return []; }

args
 = i:id _? ")" { return i; }
 / i:id _? "," _? o:args { return [i,o]; }

funcBody
 = "{" __? s:statements __? "}" { return s; }

statements
 = r:statementReturn { return r; }
 / a:statementAssign ___ s:statements { return [a,s];}

statementAssign
 = _? i:id _? "=" _? e:expression _? { return [i,e]; }

statementReturn
 = _? r:"return" _ e:expression _? { return [r,e]; }

_
 = [ \t]+ { return " "; }

__
 = [ \t\n]+ { return " "; }

___
 = "\n"+ { return " "; }

expression
 = a:atom _? o:[-+*/] _? e:expression { return a+o+e; }
 / "(" e:expression ")" { return ["(",e,")"]; }
 / atom

atom
 = id
 / num

id
 = letters:[A-z]+ { return letters.join(""); }

num
 = digits:[0-9]+ { return digits.join(""); }