From fed70f3ac817ed4943a230cb901fcd65dc6fdd0c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ma=C3=ABl=20Gassmann?= <mael.gassmann@students.bfh.ch>
Date: Fri, 11 Jun 2021 20:55:12 +0200
Subject: [~] First totaly functional Calculator, reorganised the files,
 verified and added error messages

---
 .../main/java/ch/bfh/parser/ExpressionParser.java  | 36 ++++++++++------------
 1 file changed, 17 insertions(+), 19 deletions(-)

(limited to 'calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java')

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 3ec0194..e68983b 100644
--- a/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java
+++ b/calculator-java/src/main/java/ch/bfh/parser/ExpressionParser.java
@@ -1,22 +1,15 @@
 package ch.bfh.parser;
 
-import ch.bfh.CalculatorLexer;
-import ch.bfh.Token;
-import ch.bfh.exceptions.ParserException;
-
+import ch.bfh.lexer.CalculatorLexer;
+import ch.bfh.lexer.Token;
 import java.util.ArrayList;
 
-public class ExpressionParser extends Parser {
+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();
-    }
-
     protected ExpressionParser(CalculatorLexer cl, Token lastToken, boolean isParenthesised) {
         this.cl = cl;
         this.lastToken = lastToken;
@@ -31,8 +24,8 @@ public class ExpressionParser extends Parser {
             token = lastToken;
         else
             token = cl.nextToken();
-        Parser l = null;
-        Parser r = null; // left and right expressions
+        TermParser l = null;
+        TermParser r = null; // left and right Terms
         Token op = null; // operation of the current l and right expressions
 
         loop:
@@ -48,9 +41,9 @@ public class ExpressionParser extends Parser {
                         op = token;
                         this.ops.add(op);
                     }else if (l == null)
-                        throw new ParserException("Factor cannot start with '+'.");
+                        throw new ParserException("Redundant use of '+' is forbidden.");
                     else
-                        throw new ParserException("Invalid use of '+' was found in the Expression.");
+                        throw new ParserException(token, "repetition of operator -> a term was expected.");
                     break;
                 case Token.SUB:
                     if (l != null && op == null) { // if the '-' sign is between two term (op)
@@ -82,14 +75,19 @@ public class ExpressionParser extends Parser {
                         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.");
+                case Token.MUL:
+                case Token.DIV:
+                    throw new ParserException(token,"a term was expected.");
+                case Token.EQU:
+                case Token.LET:
+                    throw new ParserException("The inputted token '"+token.str+"' can only be placed in a variable declaration context (let var = Expression).");
+                case Token.END:
+                    throw new ParserException("The keyword 'exit' can only be placed at the beginning of an expression.");
             }
             token = cl.nextToken();
         }
         if (op != null && r == null)
-            throw new ParserException("Missing expression after last operation '"+op.str+"'");
+            throw new ParserException("Missing term after the last operator '"+op.str+"'.");
     }
 
     @Override
@@ -111,4 +109,4 @@ public class ExpressionParser extends Parser {
         }
         return result;
     }
-}
+}
\ No newline at end of file
-- 
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