Indexing into Function Call Results
This topic describes how to dot index into temporary variables created by function calls. A temporary
variable is created when the result of a function call is used as an intermediate variable in a larger
expression. The result of the function call in the expression is temporary because the variable it
creates exists only briefly, and is not stored in the MATLAB workspace after execution. An example is
the expression myFunction(x).prop, which calls myFunction with the argument x, and then
returns the prop property of the result. You can invoke any type of function (anonymous, local,
nested, or private) in this way.
Example
Consider the function:
function y = myStruct(x)
y = struct("Afield",x);
end
This function creates a structure with one field, named Afield, and assigns a value to the field. You
can invoke the function and create a structure with a field containing the value 1 with the command:
myStruct(1)
ans =
struct with fields:
Afield: 1
However, if you want to return the field value directly, you can index into the function call result with
the command:
myStruct(1).Afield
ans =
1
After this command executes, the temporary structure created by the command myStruct(1) no
longer exists, and MATLAB returns only the field value. Conceptually, this usage is the same as
creating the structure, indexing into it, and then deleting it:
S = struct("Afield",1);
S.Afield
clear S
Supported Syntaxes
MATLAB supports dot indexing into function call results, as in foo(arg).prop. Other forms of
indexing into function call results (with parentheses such as foo(arg)(2) or with curly braces such
as foo(arg){2}) are not supported. Successful commands must meet the criteria:
• The function is invoked with parentheses, as in foo(arg1,arg2,...).
• The function returns a variable for which dot indexing is defined, such as a structure, table, or
object.
20 Function Basics
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