Yashwanth Raj

Hi.,
In comparison with the parser i have done in my previous post
https://coderanch.com/t/630884/java/java/recursive-descent-parsing ,
is this a good implementation
package parser; import static parser.OpType.*; enum OpType { EMPTY, END, UNKNOWN, NUMBER, IDENT, PLUS, MINUS, STAR, SLASH, MOD } public class SimpleParser { String exp; OpType type; double currNum; int i; public SimpleParser(String e) { type= OpType.UNKNOWN; currNum= 0; i=0; exp=e; } double getNum() { StringBuffer buffer=new StringBuffer(""); while((i<exp.length()&&(Character.isDigit(exp.charAt(i))||exp.charAt(i)=='.'))) { buffer.append(exp.charAt(i)); i++; } return Double.valueOf(new String(buffer)); } OpType getNext() { if(exp.length()==0) { return EMPTY; } while(i<exp.length()&&(exp.charAt(i)==' ')) { if(++i<exp.length()){i++;} } if(i<exp.length()&&Character.isDigit(exp.charAt(i))) { currNum=getNum(); return NUMBER; } else if(i<exp.length()&&(exp.charAt(i)=='+'||exp.charAt(i)=='-'|| exp.charAt(i)=='*'||exp.charAt(i)=='/'||exp.charAt(i)=='%')) { char c=exp.charAt(i); if(++i<exp.length()); switch(c) { case '+': return PLUS; case '-': return MINUS; case '*': return STAR; case '/': return SLASH; case '%': return MOD; } } if(i++==exp.length()) { return END; } return UNKNOWN; } double evalNum() { double d=2; type=getNext(); if(type==NUMBER) { d=currNum; type=getNext(); } return d; } double evalMul() { double d=evalNum(); while(type==STAR||type==SLASH||type==MOD) { if(type==MOD) { d%=evalNum(); } else if(type==SLASH) { d/=evalNum(); } else if(type==STAR) { d*=evalNum(); } } return d; } double evalPlus() { double d=evalMul(); if(type==MINUS) { d=-evalMul(); } while(type==PLUS||type==MINUS) { if(type==PLUS) { d+=evalMul(); } else if(type==MINUS) { d-=evalMul(); } } return d; } double test() { double res=evalPlus(); return res; } public static void main(String[] args) { SimpleParser p= new SimpleParser("-7*7/7"); System.out.println(p.test()); } }
also how can i add error checking in my parser

the guy who moved the post,thanks but please answer me or warn if i ain't clear!

what symbol wasn't found...exact error msg?

i downloaded j3d plugin for netbeans. i installed it using Tools-Plugins.but its seems not to be working. any suggestions...or should i give more details.

Update:i can't see the plugin in installed tab.

one
step at a time?

???

is every other logic correct? i don't know what algorithm i've implemented

and whats that thumbs up sign.reputations?

sale class should have extended a valid JComponent class..

oops ...i posted on a wrong thread..sorry for that.

hi,i can't understand how expression parsing works..i have made a parser which doesn't use any algorithm. but recursive descent is said to be flexible...can any one explain it for mr with working example. i am confused on reasing online tutorials.my code is
package parser; public class Parser { boolean isNum(StringBuffer s) { try { Double.parseDouble(new String(s)); } catch (NumberFormatException e) { return false; } return true; } double toNum(StringBuffer s) { return Double.parseDouble(new String(s)); } double eval(StringBuffer exp) { if(isNum(exp)) { return toNum(exp); } else if(!isNum(exp)) { for(int i=exp.length()-1;i>=0;i--) { if(exp.charAt(i)=='/') { return (double)eval(new StringBuffer(exp.substring(0, i))) / eval (new StringBuffer(exp.substring(i+1,exp.length()))); } else if (exp.charAt(i)=='*') { return (double)eval(new StringBuffer(exp.substring(0, i))) * eval(new StringBuffer(exp.substring(i+1,exp.length()))); } else if (exp.charAt(i)=='-') { return (double)eval(new StringBuffer(exp.substring(0, i))) - eval(new StringBuffer(exp.substring(i+1,exp.length()))); } else if (exp.charAt(i)=='+') { return (double)eval(new StringBuffer (exp.substring(0, i))) + eval(new StringBuffer(exp.substring(i+1,exp.length()))); } } } return 0; } public static void main (String[] args) { System.out.println("Simple Expression Parser \n"); System.out.println(new Parser().eval(new StringBuffer("-1+2*3/4"))); } }

thank you.now i am done

i m setting the layout for just the panel where the buttons go .the order should be 3x3.and i also want the menu bar on top for menus like game start and game exit

sorry .it is grid layout.and not grouplayout.but when i use 'grid layout' the buttons are well arranged of order 3x3.but when i add a menu bar,it also becomes like a cube rather than like a bar on the top next to the title bar.i tried both grid and group layouts.but group layout is too complex.so is there any other layouts to arrange the buttons of order 3x3 without affecting the menubar?

hi i m new to gui in java.i am programming tictactoe game.for that i will need 9 buttons of order3x3.but how can i do it with grid layout class.i cant even set 4 buttons of correct order.please help

sir i have a doubt.you have used <>for including iostream and "" for including a user defined header.what are their difference