Added Documentation

MathPad/MPSumFunction.h

@@ -8,12 +8,54 @@
 
 #import "MPFunction.h"
 
+
+
 @class MPSumFunction, MPExpression;
 
+
+/*!
+    @class      MPSumFunction
+    @brief      A sum function (generally noted using a capital sigma) evaluates
+                a term repeatedly and sums up the results.
+ 
+    @discussion A sum function has a start and a target expression indicating how
+                often the sum expression should be evaluated. Both the value of
+                the start expression and the target expressions are included in
+                the iterations.
+ 
+                Each iteration the sum value is incremented by @c 1. If the start
+                and target expression evaluate to the same value the sum is
+                evaluated once.
+ */
 @interface MPSumFunction : MPFunction
 
-@property (nonatomic, strong) MPExpression *startExpression; // Index 0
-@property (nonatomic, strong) MPExpression *targetExpression; // Index 1
-@property (nonatomic, strong) MPExpression *sumExpression; // Index 2
+
+/*!
+    @property   startExpression
+    @brief      The value of the first iteration.
+ 
+    @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.
+ */
+@property (nonatomic, strong) MPExpression *startExpression; /* Index 0 */
+
+
+/*!
+    @property   startExpression
+    @brief      The value if the last iteration.
+ */
+@property (nonatomic, strong) MPExpression *targetExpression; /* Index 1 */
+
+
+/*!
+    @property   sumExpression
+    @brief      The sum expression evaluated multiple times.
+ 
+    @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.
+ */
+@property (nonatomic, strong) MPExpression *sumExpression; /* Index 2 */
 
 @end