java - I don't know how to implement a recursive syntax analyzer -

java - I don't know how to implement a recursive syntax analyzer -

i have next context free grammar:

e = (e) e = | ε

given input string, have determine whether string accepted grammar or not, recursive syntax analyzer. example, if have input:

((i))<- valid (((i))))<- invalid ()<- valid

and have code supposed of these

public static boolean e() { int popen; popen = 0; if (lexico.equals("(")) { popen++; e(); } else if (lexico.equals("i")) { if (popen == 0) homecoming true; //this valid else verifyparenthesis(); } } public static boolean verifyparenthesis() { int pclose = 0; while ((lexico = nextsymbol()).equals(")")) pclose++; }

but not sure how verify number of open parentheses ( same number of close parentheses ).

do have utilize while on verifyparenthesis method?

recursive with. enjoy.

public static boolean expressioniscorrect(string expr) { if(!expr.contains("(") && !expr.contains(")")) { homecoming true; } int indexofleft = -1; int indexofright = -1; indexofleft = expr.indexof("("); indexofright = expr.lastindexof(")"); if (indexofleft>=indexofright) { homecoming false; } homecoming expressioniscorrect(expr.substring(indexofleft+1, indexofright)); }

don't hesitate inquire question if don't understand what's going on, seek first.

java parsing context-free-grammar