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POIdentifying Unary minus in calculator, java
 

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    <p>Hi guys i'm almost done writing my code and i'm stuck with this stupid thing. I can identify cases in which there's a unary minus before brackets (-[4 + 4]). here's my code:</p> <pre><code>package oop.ex2.expression; import java.io.IOException; import java.util.HashMap; import oop.ex2.exception.*; import oop.ex2.main.Tokenizer; /** * This class contains 3 public static methods. All 3 methods are used * to parse text into a mathematical expression. The information is "thrown" * back and forth from one method to another. */ public class ExpressionParser { /** * This method uses expression() method to parse the text into mathematical * expressions, and returns an expression which is the sum of all * expressions returned from expression() [the sum is calculated according * to the right operator] * * @param st - the Tokenizer parsing the text * @return - Expression, the sum of all expressions from expression() * @throws InputException * @throws IOException */ public static Expression sumExpressions(Tokenizer st) throws InputException, IOException { boolean endOfLine = false; Expression temp = expression(st); int token = Tokenizer.TT_NOTHING; while (!endOfLine) { token = st.nextToken(); if ((token == Tokenizer.TT_OPERATOR) || (token == Tokenizer.TT_OVERLOADED_OP)) temp = new FatherExpression(st.op, temp, expression(st)); else endOfLine = true; } return temp; } public static Expression expression(Tokenizer st) throws InputException, IOException { Expression result = null; switch (st.nextToken()) { case Tokenizer.TT_NUMBER: result = new NumberExpression(st.nval); break; case Tokenizer.TT_VARIABLE: result = new VariableExpression(st.sval); break; case Tokenizer.TT_FUNC: result = createFunction(st); break; case '[': result = sumExpressions(st); if (st.ttype != ']') throw new BracketException("BracketException: " + "one too many ']'"); break; default: throw new UnexpectedTokenException("Unexpected token on" + "ExpressionParser.elements(st)"); } return result; } private static Expression createFunction(Tokenizer st) throws IOException, InputException { if (InlineManager.getAllInlineFunctions().containsKey(st.sval)) { InlineFunction temp = InlineManager.getInlineFunction(st.sval); temp.setArguments(st); return temp; } if (st.sval.equals("MAX")) return new Max(st); if (st.sval.equals("MIN")) return new Min(st); if (st.sval.equals("POW")) return new Pow(st); if (st.sval.equals("MOD")) return new Mod(st); if (st.sval.equals("ABS")) return new Abs(st); throw new FunctionNameException("Wrong funcion entred " + st.sval); } public static HashMap&lt;String, Expression&gt; parseArguments(Tokenizer st) throws IOException, InputException { HashMap&lt;String, Expression&gt; result = new HashMap&lt;String, Expression&gt;(); if (st.nextToken() != '{') throw new UnexpectedTokenException("Missing {"); int argument = 0; while (true) { st.ignoreToken(',', true); switch (st.nextToken()) { case '}': st.ignoreToken(',', false); return result; case '[': result.put(String.valueOf(argument++), sumExpressions(st)); break; case Tokenizer.TT_NUMBER: result.put(String.valueOf(argument++), new NumberExpression(st.nval)); break; case Tokenizer.TT_VARIABLE: result.put(String.valueOf(argument++), new VariableExpression(st.sval)); break; case Tokenizer.TT_FUNC: result.put(String.valueOf(argument++), createFunction(st)); break; default: throw new UnexpectedTokenException("Unexpected token on function arguments"); } } } } </code></pre> <p>it long i know. Expression object could be a constant, a variable or a function such as MAX{3,2} which is 3. expression() uses a tokenizer i have built to parse text into an expression, and sumExpression() uses expression() to create a new Expression which is a combination of two Expression object according to the right operator.</p> <p>i hope its clear. as i said before i can't figure out how to identify the unary minus (-[4] would be -4) thing. i didn't put my tokenizer code, didn't think its necessary.</p> <p>thanks! </p> <p>P.S. the order of calculations is defined to be left to right with no regards to type of operator.</p>
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