Added/Corrected Documentation

MathPad/MPSumFunction.h

@@ -6,6 +6,13 @@
 //  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
 //
 
+/*!
+ @header
+ This is a description of the MPFunction class.
+ 
+ It has multiple lines.
+ */
+
 #import "MPFunction.h"
 
 
@@ -15,8 +22,8 @@
 
 /*!
     @class      MPSumFunction
-    @brief      A sum function (generally noted using a capital sigma) evaluates
-                a term repeatedly and sums up the results.
+    @brief      This class represents a sum function (generally noted using a
+                capital sigma).
  
     @discussion A sum function has a start and a target expression indicating how
                 often the sum expression should be evaluated. Both the value of
@@ -37,13 +44,16 @@
     @discussion The start expression must define a variable that may be used in
                 the sum expression. If the start expression does not define a
                 variable the sum function will fail on validation.
+    @code       Some samples
  */
 @property (nonatomic, strong) MPExpression *startExpression; /* Index 0 */
 
 
 /*!
-    @property   startExpression
+    @property   targetExpression
     @brief      The value if the last iteration.
+ 
+    @discussion The target expression must not define a variable.
  */
 @property (nonatomic, strong) MPExpression *targetExpression; /* Index 1 */
 
@@ -55,6 +65,8 @@
     @discussion During evaluation of the sum expression the variable defined in
                 the start expression is available. That variable always contains
                 the value of the current iteration.
+ 
+                The sum expression itself must not define a variable.
  */
 @property (nonatomic, strong) MPExpression *sumExpression; /* Index 2 */