diff options
author | Maël Gassmann <mael.gassmann@students.bfh.ch> | 2021-06-11 17:28:55 +0200 |
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committer | Maël Gassmann <mael.gassmann@students.bfh.ch> | 2021-06-11 17:28:55 +0200 |
commit | 98ddff97ec1d092b18ef2d176e83bd92f9671e03 (patch) | |
tree | af1457e05063421dc2860e6c033e58b28f9a8e4e /calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java | |
parent | 49f30529d9cd2ed62902079a45d4d3c1f45afbda (diff) |
[+] Added StatementParser, [~] Restructured the Parsers
Diffstat (limited to 'calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java')
-rw-r--r-- | calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java | 180 |
1 files changed, 10 insertions, 170 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 index f96353e..3ec0194 100644 --- a/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java +++ b/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java @@ -10,21 +10,27 @@ public class ExpressionParser extends Parser { protected ArrayList<Parser> parsers = new ArrayList<>(); protected ArrayList<Token> ops = new ArrayList<>(); + private boolean isParenthesised = false; public ExpressionParser(CalculatorLexer cl) { this.cl = cl; parse(); } - private ExpressionParser(CalculatorLexer cl, Token lastToken) { + protected ExpressionParser(CalculatorLexer cl, Token lastToken, boolean isParenthesised) { this.cl = cl; this.lastToken = lastToken; - parse(); + this.isParenthesised = isParenthesised; //If an expression starts with the lastToken set as '(' it could mean that the Expression first term will be a parenthesised expression + parse(); //But it could also mean that this Expression is the parenthesised one, that is why this variable is required. } @Override protected void parse() { - Token token = cl.nextToken(); + Token token; + if(lastToken != null && !isParenthesised) + token = lastToken; + else + token = cl.nextToken(); Parser l = null; Parser r = null; // left and right expressions Token op = null; // operation of the current l and right expressions @@ -58,6 +64,7 @@ public class ExpressionParser extends Parser { this.ops.add(op); } // Then the '-' is the start of a new expression and not an operation case Token.PAL: + case Token.ID: case Token.NUM: if (l == null) { l = new TermParser(cl, token); @@ -104,171 +111,4 @@ public class ExpressionParser extends Parser { } 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) - if (isNegative) - return expression.getValue()*(-1); - else - return expression.getValue(); - if (isNegative) - return value*(-1); - return value; - } - } - } } |