Added Documentation

MathPad/MPExpressionElement.h

@@ -6,11 +6,52 @@
 //  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
 //
 
+
+
+/*!
+    @protocol   MPExpressionElement
+    @brief      This protocol defines the functionality an element in an
+                expression must have.
+ */
 @protocol MPExpressionElement <NSObject, NSCopying, NSCoding>
 
+
+/*!
+    @method     isString
+    @brief      Returns wether the receiver is a string.
+ 
+    @discussion A string is defined by being an instance of @c NSString. If this
+                method returns @c YES you can be sure it is an @c NSString
+                instance.
+ 
+    @return     @c YES if the receiver is a string, @c NO otherwise.
+ */
 - (BOOL)isString;
+
+
+/*!
+    @method     isFunction
+    @brief      Returns wether the receiver is a function.
+ 
+    @discussion A function is defined by being an instance of @c MPFunction. If
+                this method returns @c YES you can be sure it is a @c MPFunction
+                instance.
+ 
+    @return     @c YES if the receiver is a function, @c NO otherwise.
+ */
 - (BOOL)isFunction;
 
+
+/*!
+    @method     length
+    @brief      Calculates the length of the receiver.
+ 
+    @discussion The length of a @c MPExpressionElement is the number of symbols
+                it consists of. For strings this is the number of characters in
+                it. Functions have a length of @c 1.
+
+    @return     The receiver's length.
+ */
 - (NSUInteger)length;
 
 @end