[+] First version of the java calculator

1 files changed, 270 insertions, 0 deletions

diff --git a/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java b/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java
new file mode 100644
index 0000000..229e700
--- /dev/null
+++ b/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java
@@ -0,0 +1,270 @@
+package ch.bfh.parser;
+
+import ch.bfh.CalculatorLexer;
+import ch.bfh.Token;
+import ch.bfh.exceptions.ParserException;
+
+import java.util.ArrayList;
+
+public class ExpressionParser extends Parser {
+
+    protected ArrayList<Parser> parsers = new ArrayList<>();
+    protected ArrayList<Token> ops = new ArrayList<>();
+
+    public ExpressionParser(CalculatorLexer cl) {
+        this.cl = cl;
+        parse();
+    }
+
+    private ExpressionParser(CalculatorLexer cl, Token lastToken) {
+        this.cl = cl;
+        this.lastToken = lastToken;
+        parse();
+    }
+
+    @Override
+    protected void parse() {
+        Token token = cl.nextToken();
+        Parser l = null;
+        Parser r = null; // left and right expressions
+        Token op = null; // operation of the current l and right expressions
+
+        loop:
+        while (token != null && token.type != Token.EOL) {
+            switch (token.type) {
+                case Token.ADD: // '+' is not authorised if not op
+                    if (l != null && op == null) { // if the '+' sign is between two term (op)
+                        op = token;
+                        this.ops.add(op);
+                    } else if (l != null && r != null) { // if we already found a 'l op r' we roll
+                        l = r;
+                        r = null;
+                        op = token;
+                        this.ops.add(op);
+                    }else if (l == null)
+                        throw new ParserException("Factor cannot start with '+'.");
+                    else
+                        throw new ParserException("Invalid use of '+' was found in the Expression.");
+                    break;
+                case Token.SUB:
+                    if (l != null && op == null) { // if the '-' sign is between two term (op)
+                        op = token;
+                        break;
+                    } else if (l != null && r != null) { // if we already found a 'l op r' we roll
+                        l = r;
+                        r = null;
+                        op = token;
+                        this.ops.add(op);
+                    } // Then the '-' is the start of a new expression and not an operation
+                case Token.PAL:
+                case Token.NUM:
+                    if (l == null) {
+                        l = new TermParser(cl, token);
+                        this.parsers.add(l);
+                        token = l.lastToken;
+                    } else {
+                        r = new TermParser(cl, token);
+                        this.parsers.add(r);
+                        token = r.lastToken;
+                    }
+                    continue loop;
+                case Token.PAR:
+                    if (lastToken.type == Token.PAL) { // if equal to '(' it means it was created by a Factor
+                        lastToken = token;
+                        break loop;
+                    } else
+                        throw new ParserException("No matching opening parenthesis were found.");
+                default:
+                    //TODO - Replace default by each individual case
+                    throw new ParserException("Malformed Expression.");
+            }
+            token = cl.nextToken();
+        }
+        if (op != null && r == null)
+            throw new ParserException("Missing expression after last operation '"+op.str+"'");
+    }
+
+    @Override
+    public double getValue(){
+        double result = 0.0;
+        if (!this.parsers.isEmpty()) {
+            result = this.parsers.get(0).getValue();
+
+            for (int i = 1; i < this.parsers.size(); i++) {
+                switch (this.ops.get(i-1).type){
+                    case Token.ADD:
+                        result += this.parsers.get(i).getValue();
+                        break;
+                    case Token.SUB:
+                        result -= this.parsers.get(i).getValue();
+                        break;
+                }
+            }
+        }
+        return result;
+    }
+
+    private class TermParser extends ExpressionParser {
+
+        public TermParser(CalculatorLexer cl, Token lastToken) {
+            super(cl, lastToken);
+        }
+
+        @Override
+        protected void parse() {
+            Token token = lastToken;
+            lastToken = null;
+            Parser l = null;
+            Parser r = null; // left and right expressions
+            Token op = null; // operation of the current l and right expressions
+
+            loop:
+            while (token != null && token.type != Token.EOL) {
+                switch (token.type) {
+                    case Token.ADD:
+                        if (op != null) {
+                            lastToken = token;
+                            break loop; // going here on case 'n/+...' or 'n*+...' since '+' would be invalid
+                        }
+                    case Token.SUB:
+                    case Token.NUM:
+                    case Token.PAL:
+                        if (l == null) {
+                            l = new FactorParser(cl, token);
+                            this.parsers.add(l);
+                            token = l.lastToken;
+                            continue loop;
+                        } else if (op != null) {
+                            r = new FactorParser(cl, token);
+                            this.parsers.add(r);
+                            token = r.lastToken;
+                            lastToken = token; // in case we finished
+                            continue loop;
+                        } else {
+                            lastToken = token;
+                            break loop; // going here on case 'n+...' or 'n-...' since '+' and '-' are part of the parent expression
+                        }
+                    case Token.MUL:
+                    case Token.DIV:
+                        if (l != null && op == null) { // if the '*' or '/' signs are between two Factors (op)
+                            op = token;
+                            this.ops.add(op);
+                        } else if (l != null && r != null) { // if we already found a 'l op r' we roll
+                            l = r;
+                            r = null;
+                            op = token;
+                            this.ops.add(op);
+                        } else
+                            throw new ParserException("Two '" + token.str + "' in a row were found.");
+                        break;
+                    case Token.PAR:  // Going as high as possible --> possibly the end of an expression created by a Factor :)
+                        lastToken = token;
+                        break loop;
+                    default:
+                        //TODO - Replace default by each individual case
+                        throw new ParserException("Malformed Expression.");
+                }
+                token = cl.nextToken();
+            }
+            if (op != null && r == null)
+                throw new ParserException("Missing expression after last operation '"+op.str+"'");
+        }
+
+        @Override
+        public double getValue(){
+            double result = 0.0;
+            if (!this.parsers.isEmpty()) {
+                result = this.parsers.get(0).getValue();
+
+                for (int i = 1; i < this.parsers.size(); i++) {
+                    switch (this.ops.get(i-1).type){
+                        case Token.MUL:
+                            result *= this.parsers.get(i).getValue();
+                            break;
+                        case Token.DIV:
+                            result /= this.parsers.get(i).getValue();
+                            break;
+                    }
+                }
+            }
+            return result;
+        }
+
+        private class FactorParser extends Parser {
+
+            ExpressionParser expression; // only used when parenthesis are found
+            boolean isNegative = false;
+            boolean somethingWasParsed = false;
+
+            public FactorParser(CalculatorLexer cl, Token lastToken) {
+                this.cl = cl;
+                this.lastToken = lastToken;
+                parse();
+            }
+
+            @Override
+            protected void parse() {
+                Token token = lastToken;
+                lastToken = null;
+                loop:
+                while (token != null && token.type != Token.EOL) {
+                    switch (token.type) {
+                        case Token.MUL:
+                        case Token.DIV:
+                        case Token.ADD:
+                            if (somethingWasParsed) { // finished parsing the Factor
+                                lastToken = token; // sending the token to the parent
+                                break loop;
+                            } else
+                                throw new ParserException("Empty expression before '" + token.str + "'.");
+                        case Token.SUB:
+                            if (!somethingWasParsed)
+                                if (!isNegative)
+                                    isNegative = true;
+                                else
+                                    throw new ParserException("A factor cannot contain two '-'.");
+                            else { // Meaning we could have parsed '-4' or '4' and '-' is the next digit which is op for the overall expression
+                                lastToken = token;
+                                break loop;
+                            }
+                            break;
+                        case Token.NUM:
+                            if (!somethingWasParsed) {
+                                value = token.value;
+                                somethingWasParsed = true;
+                            } else
+                                throw new ParserException("Missing operator between the two Factors.");
+                            break;
+                        case Token.PAL:
+                            if (!somethingWasParsed) {
+                                expression = new ExpressionParser(cl, token);
+                                if (expression.lastToken.type != Token.PAR)
+                                    throw new ParserException("No matching closing parenthesis were found.");
+                                somethingWasParsed = true;
+                            } else
+                                throw new ParserException("Missing operator between the two Factors.");
+                            break;
+                        case Token.PAR:  // Going as high as possible --> possibly the end of an expression created by a Factor :)
+                            if (somethingWasParsed)
+                                lastToken = token;
+                            else throw new ParserException("Missing expression before closing the parenthesis.");
+                            break loop;
+                        default:
+                            //TODO - Replace default by each individual case
+                            throw new ParserException("Malformed Expression.");
+                    }
+                    token = cl.nextToken();
+                }
+            }
+
+            @Override
+            public double getValue(){
+                if (expression != null)
+                    return expression.getValue();
+                if (isNegative)
+                    return value*(-1);
+                return value;
+            }
+        }
+    }
+}