expanded Value interface

src/com/bytezone/diskbrowser/visicalc/Cell.java

@@ -2,19 +2,17 @@ package com.bytezone.diskbrowser.visicalc;
 
 class Cell implements Comparable<Cell>, Value
 {
-  //  private static final Pattern cellContents =
-  //      Pattern.compile ("([-+/*]?)(([A-Z]{1,2}[0-9]{1,3})|([0-9.]+)|(@[^-+/*]+))");
-
   final Address address;
   private final Sheet parent;
 
-  private String label;
   private char format = ' ';
   private char repeatingChar;
   private String repeat = "";
 
+  private String label;
   private String expressionText;
-  private Expression expression;
+  private Value value;
+  //  private boolean hasValue;
 
   public Cell (Sheet parent, Address address)
   {
@@ -44,7 +42,7 @@ class Cell implements Comparable<Cell>, Value
       System.out.printf ("Unexpected format [%s]%n", format);
   }
 
-  void doCommand (String command)
+  void setValue (String command)
   {
     switch (command.charAt (0))
     {
@@ -92,12 +90,6 @@ class Cell implements Comparable<Cell>, Value
         expressionText = "11.9";
       else if (address.sortValue == 579)
         expressionText = "D9*G5/(1-((1+G5)^-D4))";
-
-  }
-
-  boolean hasValue ()
-  {
-    return expressionText != null;
   }
 
   char getFormat ()
@@ -105,6 +97,7 @@ class Cell implements Comparable<Cell>, Value
     return format;
   }
 
+  // this should be called by Sheet when drawing, so do all formatting here
   String getText ()
   {
     if (label != null)
@@ -114,20 +107,44 @@ class Cell implements Comparable<Cell>, Value
     return "?";
   }
 
+  @Override
+  public boolean hasValue ()
+  {
+    if (label != null || repeatingChar > 0)
+      return false;
+
+    if (value == null)
+      createValue ();
+    return value.hasValue ();
+  }
+
+  // this should be called when doing calculations
   @Override
   public double getValue ()
   {
-    if (expression == null)
+    if (value == null)
+      createValue ();
+    return value.getValue ();
+  }
+
+  @Override
+  public String getError ()
+  {
+    if (value == null)
+      createValue ();
+    return hasValue () ? "" : "@NA";
+  }
+
+  private void createValue ()
+  {
+    if (expressionText == null)
     {
-      if (expressionText == null)
+      System.out.printf ("%s null expression text %n", address);
-      {
+      value = Function.getInstance (parent, "@ERROR()");
-        System.out.printf ("%s null expression text %n", address);
-        return 0;
-      }
-      //      System.out.printf ("%s Instantiating [%s]%n", address, expressionText);
-      expression = new Expression (parent, expressionText);
     }
-    return expression.getValue ();
+    else
+      //      System.out.printf ("%s Instantiating [%s]%n", address, expressionText);
+      value = new Expression (parent, expressionText);
   }
 
   @Override

src/com/bytezone/diskbrowser/visicalc/Expression.java

@@ -10,9 +10,8 @@ public class Expression implements Value
   //   cell address
   //   function
   //   expression [+-*/^] expression
-  //   [+-=] expression
+  //   [+-] expression
   //   ( expression )
-  //   -expression
 
   // From the reference card:
   // Expressions are evaluated strictly from left to right except as modified by
@@ -33,34 +32,18 @@ public class Expression implements Value
   private final List<String> operators = new ArrayList<String> ();
   private final List<String> signs = new ArrayList<String> ();
 
+  private boolean hasValue;
+
   public Expression (Sheet parent, String input)
   {
-    String line = input.trim ();
-
-    //    System.out.printf ("New expression [%s]%n", input);
-
-    int leftBracket = 0;
-    int rightBracket = 0;
-
-    for (char c : input.toCharArray ())
-      if (c == '(')
-        leftBracket++;
-      else if (c == ')')
-        rightBracket++;
-
-    if (leftBracket != rightBracket)
-    {
-      System.out.printf ("**** Unbalanced brackets: left:%d, right:%d  ****%n",
-                         leftBracket, rightBracket);
-      line = "@ERROR()";
-    }
-
     //    System.out.printf ("Exp [%s]%n", line);
+    String line = checkBrackets (input);
+
     int ptr = 0;
     while (ptr < line.length ())
     {
+      // check for optional leading + or -
       char ch = line.charAt (ptr);
-
       if (ch == '-')
       {
         signs.add ("(-)");
@@ -73,6 +56,7 @@ public class Expression implements Value
           ch = line.charAt (++ptr);
       }
 
+      // check for mandatory function/sub-expression/number/cell reference
       switch (ch)
       {
         case '@':                                           // function
@@ -84,12 +68,13 @@ public class Expression implements Value
         case '(':                                           // parentheses block
           String bracketText = getFunctionText (line.substring (ptr));
           ptr += bracketText.length ();
-          bracketText = bracketText.substring (1, bracketText.length () - 1);
+          values.add (new Expression (parent,
-          values.add (new Expression (parent, bracketText));
+              bracketText.substring (1, bracketText.length () - 1)));
           break;
 
         case '#':
           System.out.printf ("Hash character [%s] in [%s]%n", ch, line);
+          ptr++;                                            // no idea
           break;
 
         default:
@@ -97,21 +82,22 @@ public class Expression implements Value
           {
             String numberText = getNumberText (line.substring (ptr));
             ptr += numberText.length ();
-            values.add (new Number (Double.parseDouble (numberText)));
+            values.add (new Number (numberText));
           }
           else if (ch >= 'A' && ch <= 'Z')                  // cell address
           {
             String addressText = getAddressText (line.substring (ptr));
             ptr += addressText.length ();
-            values.add (parent.getCell (new Address (addressText)));
+            values.add (parent.getCell (addressText));
           }
           else
           {
-            System.out.printf ("Unknown character [%s] in [%s]%n", ch, line);
+            System.out.printf ("Unexpected character [%s] in [%s]%n", ch, line);
             return;
           }
       }
 
+      // check for optional continuation operator
       if (ptr < line.length ())
       {
         ch = line.charAt (ptr);
@@ -126,6 +112,7 @@ public class Expression implements Value
     }
 
     assert values.size () > 0;
+    hasValue = true;
 
     if (false)
     {
@@ -177,12 +164,47 @@ public class Expression implements Value
     return value;
   }
 
+  @Override
+  public boolean hasValue ()
+  {
+    return hasValue;
+  }
+
+  @Override
+  public String getError ()
+  {
+    return hasValue ? "" : "Error";
+  }
+
+  private String checkBrackets (String input)
+  {
+    String line = input.trim ();
+
+    int leftBracket = 0;
+    int rightBracket = 0;
+
+    for (char c : line.toCharArray ())
+      if (c == '(')
+        leftBracket++;
+      else if (c == ')')
+        rightBracket++;
+
+    if (leftBracket != rightBracket)
+    {
+      System.out.printf ("**** Unbalanced brackets: left:%d, right:%d  ****%n",
+                         leftBracket, rightBracket);
+      return "@ERROR()";
+    }
+    return line;
+  }
+
   private String getFunctionText (String text)
   {
     int ptr = text.indexOf ('(');         // find first left parenthesis
     if (ptr < 0)
       return "";
     int depth = 1;
+
     while (++ptr < text.length ())        // find matching right parenthesis
     {
       if (text.charAt (ptr) == ')')

src/com/bytezone/diskbrowser/visicalc/Function.java

@@ -32,6 +32,7 @@ abstract class Function implements Value
 
   Sheet parent;
   String functionText;
+  boolean hasValue;
 
   static Function getInstance (Sheet parent, String text)
   {
@@ -78,6 +79,18 @@ abstract class Function implements Value
     this.functionText = text.substring (pos + 1, text.length () - 1);
   }
 
+  @Override
+  public boolean hasValue ()
+  {
+    return hasValue;
+  }
+
+  @Override
+  public String getError ()
+  {
+    return hasValue ? "" : "Error";
+  }
+
   protected Range getRange (String text)
   {
     Range range = null;

src/com/bytezone/diskbrowser/visicalc/Number.java

@@ -1,12 +1,21 @@
 package com.bytezone.diskbrowser.visicalc;
 
-public class Number implements Value
+class Number implements Value
 {
-  private final double value;
+  private double value;
+  private boolean hasValue;
 
-  public Number (double value)
+  public Number (String text)
   {
-    this.value = value;
+    try
+    {
+      this.value = Double.parseDouble (text);
+      hasValue = true;
+    }
+    catch (NumberFormatException e)
+    {
+      hasValue = false;
+    }
   }
 
   @Override
@@ -20,4 +29,16 @@ public class Number implements Value
   {
     return String.format ("Number: %f", value);
   }
+
+  @Override
+  public boolean hasValue ()
+  {
+    return hasValue;
+  }
+
+  @Override
+  public String getError ()
+  {
+    return hasValue ? "" : "@NA";
+  }
 }

src/com/bytezone/diskbrowser/visicalc/Sheet.java

@@ -309,18 +309,21 @@ public class Sheet implements Iterable<Cell>
     if (!command.isEmpty ())
       currentCell.format (command);        // formatting command
     if (!line.isEmpty ())
-      currentCell.doCommand (line);           // expression
+      currentCell.setValue (line);           // expression
+  }
+
+  Cell getCell (String addressText)
+  {
+    Address address = new Address (addressText);
+    return getCell (address);
   }
 
   Cell getCell (Address address)
   {
     Cell cell = sheet.get (address.sortValue);
     if (cell == null)
-    {
-      //      cell = new Cell (this, address);
-      //      sheet.put (address.sortValue, cell);
       System.out.printf ("Nonexistent cell requested [%s]%n", address);
-    }
+
     return cell;
   }
 

src/com/bytezone/diskbrowser/visicalc/Value.java

@@ -2,5 +2,9 @@ package com.bytezone.diskbrowser.visicalc;
 
 public interface Value
 {
+  public boolean hasValue ();
+
   public double getValue ();
+
+  public String getError ();
 }