[~] Handling illegal tokens and writing correct error messages

1 files changed, 182 insertions, 154 deletions

diff --git a/calculator-javacc/Calculator.jj b/calculator-javacc/Calculator.jj
index cc22b0a..770bf4c 100644
--- a/calculator-javacc/Calculator.jj
+++ b/calculator-javacc/Calculator.jj
@@ -1,155 +1,183 @@
-options{
-    //DEBUG_PARSER = true; DEBUG_TOKEN_MANAGER = true;
-}
-
-PARSER_BEGIN(Calculator)
-import java.util.HashMap;
-
-public class Calculator {
-
-    private static HashMap variables = new HashMap();
-
-    public static void main(String[] args) {
-        Calculator parser = new Calculator(System.in);
-        while (true){
-            System.out.print("Type your expression: ");
-            try{
-                double value = parser.evaluateNextLine();
-                System.out.println("Returned: " + value);
-            }catch (ParseException e){
-                System.out.println(e.getMessage());
-                try{
-                    parser.passStatement(); // wiping the tokens of the malformed expression
-                }catch (ParseException ex){
-                    System.out.println(ex.getMessage());
-                }
-            }
-        }
-    }
-}
-PARSER_END(Calculator)
-
-SKIP : {
-    " "|"\t"
-}
-
-TOKEN : {
-	<EOL: "\n"|"\r">|
-	<PAL: "(">|
-	<PAR: ")">|
-	<ADD: "+">|
-	<SUB: "-">|
-	<MUL: "*">|
-	<DIV: "/">|
-	<EQU: "=">|
-	<LET: "let">|
-	<END: "exit">|
-    <NUM: (["0"-"9"])+("."((["0"-"9"])+))?>|
-	<ID: (["a"-"z"]|["A"-"Z"])+>
-}
-
-double statement() :
-{
-    Token id;
-    double i = 0.0;
-}
-{
-    <END> { System.exit(0); }|
-    i=expression() { return i; }|
-    <LET> id=<ID> <EQU> i=expression()
-        {
-            variables.put(id.image,i); //Storing the variable
-            return i;
-        }
-}
-
-double expression() :
-{
-    Token op = null;
-    double l = 0.0;
-    double r = 0.0;
-}
-{
-    l=term() ((op=<ADD> | op=<SUB>)  r=term()
-        { // folding everything in the l variable
-            if (op != null){
-                if (op.image.equals("+"))
-                    l += r;
-                else
-                    l -= r;
-            }
-
-        }
-        )*
-        { //returning the parsed value
-            return l;
-        }
-}
-
-double term() :
-{
-    Token op = null;
-    double l = 0.0;
-    double r = 0.0;
-}
-{
-    l=factor() ((op=<DIV> | op=<MUL>)  r=factor()
-        { // folding everything in the l variable
-            if (op != null){
-                if (op.image.equals("/"))
-                    l /= r;
-                else
-                    l *= r;
-            }
-
-        }
-        )*
-        { //returning the parsed value
-            return l;
-        }
-}
-
-double factor() :
-{
-    Token t = null;
-    Token id = null;
-    double i = 0.0;
-}
-{
-    (t=<NUM> | id=<ID> | <PAL> (i=expression())? <PAR>)
-        {
-            if(id != null){
-                Object var = variables.get(id.image);
-                if (var != null)
-                    i = (double) var;
-                else
-                    throw new ParseException("'" + id.image + "' is not yet defined.");
-            }else if(t != null)
-                i = Double.parseDouble(t.image);
-            return i;
-        }|
-    <SUB> (t=<NUM> | id=<ID> | <PAL> (i=expression())? <PAR>)
-    {
-            if(id != null){
-                i = (double)variables.get(id.image);
-            }else if(t != null)
-                i = Double.parseDouble(t.image);
-        return i*(-1);
-    }
-}
-
-double evaluateNextLine() :
-{
-    double result = 0.0;
-}
-{
-	(result=statement())? <EOL> {return result;}|
-	<EOF>{System.out.println("\nBuffer was closed. Exiting."); System.exit(0);}
-}
-
-void passStatement() :
-{}
-{
-    <EOL>|
-	<EOF>{System.out.println("\nBuffer was closed. Exiting."); System.exit(0);}
+options{

+    //DEBUG_PARSER = true; DEBUG_TOKEN_MANAGER = true;

+}

+

+PARSER_BEGIN(Calculator)

+import java.util.HashMap;

+

+public class Calculator {

+

+    private static HashMap variables = new HashMap();

+

+    public static void main(String[] args) {

+        Calculator parser = new Calculator(System.in);

+        while (true){

+            System.out.print("Type your expression: ");

+            try{

+                double value = parser.evaluateNextLine();

+                System.out.println("Returned: " + value);

+            }catch (ParseException e){  // Now we will parse the exception message to render it in our format.

+                int index = "Encountered: \"".length();

+                String em = e.getMessage().substring(index);

+                String token = em.substring(1,4);

+

+                if (token.equals("ILL")){

+                    em = em.substring(7);

+                    index = em.indexOf("\"")-1;

+                    if (index == 0){ // Special case in which the illegal token would be '"'

+                        index = 2;

+                    }

+                    System.out.println("Illegal token: '"+ em.substring(0 , index) +"'.");

+                }else if(token.equals("EOL")){

+                    System.out.println("Last read token: '<EOL>', w"+em.substring(em.indexOf("\nW")+2));

+                }else if(em.split("\n").length > 1){

+                    index = em.indexOf("\"");

+                    if (index == 0){ // Meaning the last token is not <TOK> but "char"

+                        em = em.substring(1);

+                        index = em.indexOf("\"");

+                    }else{

+                        index--;

+                    }

+                    System.out.println("Last read token: '"+ em.substring(0 , index)+"', w"+em.substring(em.indexOf("\nW")+2));

+                }else{ //Those were error messages created by ourselves, they are one line messages

+                    System.out.println(e.getMessage());

+                }

+

+                try{

+                    parser.passStatement(); // wiping the tokens of the malformed expression

+                }catch (ParseException ex){

+                    System.out.println(ex.getMessage()); //not suppose to be possible to end up here

+                }

+            }

+        }

+    }

+}

+PARSER_END(Calculator)

+

+SKIP : {

+    " "|"\t"

+}

+

+TOKEN : {

+	<EOL: "\n"|"\r">|

+	<PAL: "(">|

+	<PAR: ")">|

+	<ADD: "+">|

+	<SUB: "-">|

+	<MUL: "*">|

+	<DIV: "/">|

+	<EQU: "=">|

+	<LET: "let">|

+	<END: "exit">|

+    <NUM: (["0"-"9"])+("."((["0"-"9"])+))?>|

+	<ID: (["a"-"z"]|["A"-"Z"])+>|

+	<ILL: ~[]>

+}

+

+double statement() :

+{

+    Token id;

+    double i = 0.0;

+}

+{

+    <END> { System.exit(0); }|

+    i=expression() { return i; }|

+    <LET> id=<ID> <EQU> i=expression()

+        {

+            variables.put(id.image,i); //Storing the variable

+            return i;

+        }

+}

+

+double expression() :

+{

+    Token op = null;

+    double l = 0.0;

+    double r = 0.0;

+}

+{

+    l=term() ((op=<ADD> | op=<SUB>)  r=term()

+        { // folding everything in the l variable

+            if (op != null){

+                if (op.image.equals("+"))

+                    l += r;

+                else

+                    l -= r;

+            }

+

+        }

+        )*

+        { //returning the parsed value

+            return l;

+        }

+}

+

+double term() :

+{

+    Token op = null;

+    double l = 0.0;

+    double r = 0.0;

+}

+{

+    l=factor() ((op=<DIV> | op=<MUL>)  r=factor()

+        { // folding everything in the l variable

+            if (op != null){

+                if (op.image.equals("/"))

+                    l /= r;

+                else

+                    l *= r;

+            }

+

+        }

+        )*

+        { //returning the parsed value

+            return l;

+        }

+}

+

+double factor() :

+{

+    Token t = null;

+    Token id = null;

+    double i = 0.0;

+}

+{

+    (t=<NUM> | id=<ID> | <PAL> (i=expression())? <PAR>)

+        {

+            if(id != null){

+                Object var = variables.get(id.image);

+                if (var != null)

+                    i = (double) var;

+                else

+                    throw new ParseException("'" + id.image + "' is not yet defined.");

+            }else if(t != null)

+                i = Double.parseDouble(t.image);

+            return i;

+        }|

+    <SUB> (t=<NUM> | id=<ID> | <PAL> (i=expression())? <PAR>)

+    {

+            if(id != null){

+                i = (double)variables.get(id.image);

+            }else if(t != null)

+                i = Double.parseDouble(t.image);

+        return i*(-1);

+    }

+}

+

+double evaluateNextLine() :

+{

+    double result = 0.0;

+}

+{

+	(result=statement())? <EOL> {return result;}|

+	<EOF>{System.out.println("\nBuffer was closed. Exiting."); System.exit(0);}

+}

+

+

+void passStatement() :

+{

+ }

+{

+    (<ILL>|<PAL>|<PAR>|<ADD>|<SUB>|<MUL>|<DIV>|<EQU>|<LET>|<END>|<NUM>|<ID>)* <EOL>| //Skip any token until the next EOL

+	<EOF>{System.out.println("\nBuffer was closed. Exiting."); System.exit(0);}

 }
\ No newline at end of file