//
//  MPSumFunction.h
//  MathPad
//
//  Created by Kim Wittenburg on 22.04.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#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   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