numArgumentsFromSubscript

Number of arguments from indexing methods

Syntax

n = numArgumentsFromSubscript(A,S,indexingContext)

Description

n = numArgumentsFromSubscript(A,S,indexingContext) returns the number of expected inputs to subsasgn or the number of expected outputs from subsref. The target of the indexing expression is A, and the structure S contains the details of the indexing expression. indexingContext is an enumerated value that identifies whether the indexing expression occurs in a statement, expression, or assignment.

Examples

Number of Arguments Returned from Brace Indexing

Create a 1-by-3 cell array.

C = {"one",2,'three'};

Calculate the number of expected outputs from the brace indexing statement C{1:2}. First define the substruct that describes this indexing expression.

S = substruct('{}',{1:2});

The indexing context in C{1:2} is matlab.indexing.IndexingContext.Statement. Calculate the number of expected outputs by calling numArgumentsFromSubscript with the cell array C, the substruct S, and the context.

numArgumentsFromSubscript(C,S,matlab.indexing.IndexingContext.Statement)

ans =

     2

Call the indexing statement directly to verify that it returns two arguments.

C{1:2}

ans = 

    "one"


ans =

     2

Input Arguments

A — Target of indexing expression

array

Target of indexing expression, specified as an array of any data type.

S — Indexing argument structure

structure array

Indexing argument structure, also referred to as the substruct, specified as a structure array. Each structure has two fields:

• type — Type of indexing expression, specified as "()", ".", or "{}" to indicate parentheses, dot, or brace indexing, respectively. The value can be a character vector or string scalar.

• subs — Subscript values, specified as a character vector or string for dot indexing or a cell array of index vectors for parentheses or brace indexing.

S is a scalar structure for single indexing expressions, like A{1}, or a structure array for compound indexing expressions. For example, A{1}.field(3:5) has three levels of indexing. For this expression, S is a 1-by-3 structure array:

S(1)	type: '{}' subs: {[1]}
S(2)	type: '.' subs: 'field'
S(3)	type: '()' subs: {[3 4 5]}

Data Types: struct

indexingContext — Context of indexing expression

matlab.indexing.IndexingContext enumeration object

Context of indexing expression, specified as a matlab.indexing.IndexingContext enumeration object:

• matlab.indexing.IndexingContext.Statement — The indexing expression is a standalone statement (obj.a).

• matlab.indexing.IndexingContext.Expression — The indexing expression is part of a statement, such as an argument for a function (func(obj.a)).

• matlab.indexing.IndexingContext.Assignment — The indexing expression is on the left-hand side of an assignment statement ([obj.a] = x).

  Note

  matlab.indexing.IndexingContext is the latest name for this class. The previous name, matlab.mixin.util.IndexingContext, is still supported and has the same functionality.

Tips

• You can overload subsref, subsasgn, and numArgumentsFromSubscript to customize indexing for your classes. However, for most classes authored in R2021b and later, the recommended process for customizing indexing is to inherit from some combination of matlab.mixin.indexing.RedefinesParen, matlab.mixin.indexing.RedefinesDot, and matlab.mixin.indexing.RedefinesBrace. For more information, see Customize Object Indexing.

Version History

Introduced in R2015b