//
//  MPExpressionTree.h
//  MathPad
//
//  Created by Kim Wittenburg on 09.10.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#import "MPExpressionTreeElement.h"



@class MPExpressionTree;


/*!
    @class      MPExpressionTree
    @brief      The @c MPExpressionTree class is the main interface for working
                with the mathematical representation of an expression.
 
    @discussion Expressions are represented as a tree structure of elements (all
                of which must conform to the @c MPExpressionTreeElement
                protocol). Most messages sent to instances of the @c
                MPExpressionTree class are cascaded down different parts of an
                expression in some way.
 */
@interface MPExpressionTree : NSObject <MPExpressionTreeElement>

/*!
    @property   definedVariable
    @brief      The variable this expression defines.
 
    @discussion A variable definition must be at the beginning of an expression.
                If it defines a variable it must start with a single letter
                followed by an equals sign. The single letter is the name of the
                variable that is defined.
 */
@property (nonatomic, copy) NSString *definedVariable;


/*!
    @property   summands
    @brief      The summands that make up the receiver.
 
    @discussion A expression mathematically can be interpreted as a series of
                summands. Summands are the different pars of an expression that
                are separated by + or - symbols. Every object in the returned
                array is guaranteed to conform to the @c MPExpressionTreeElement
                protocol.
 */
@property (readonly, nonatomic, strong) NSArray *summands;


/*!
    @method     validateExpectingVariableDefinition:error:
    @brief      Validates the receiver.
 
    @discussion Using this method you can validate an expression that contains a
                variable definition. If a variable definition is expected but not
                found this method returns @c NO. Likewise @c NO is returned if
                you do not expect a variable definition but one is found.
 
    @param      flag
                Specifies wether or not to expect a variable definition at the
                beginning of the expression.
 
    @param      error
                If there is a syntax error in the receiver this parameter will be
                set to an appropriate value. If you are not interested in the
                type of syntax error pass @c NULL.
 
    @return     @c YES if the receiver is valid, @c NO otherwise. If @c NO is
                returned the @c error parameter should be set to an appropriate
                value.
 */
- (BOOL)validateExpectingVariableDefinition:(BOOL)flag
                                      error:(NSError *__autoreleasing *)error;

@end