//
//  MPExpressionElement.h
//  MathPad
//
//  Created by Kim Wittenburg on 10.08.14.
//  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