Another Matlab 2021a change to format, it optionally outputs one argument which is a 'DisplayformatOptions' containing the NumericFormat and LineSpacing properties set by format. calling format with one of these objects as input will set the state to that stored in the object.

compatable behavior could probably be trivially implemented by outputing a struct with the right fields, and setting them accordingly if you get an isstruct on the input arguments. Or slightly better by creating a simple DisplayFormatOptions class overloading format to do the same thing.

But this new output behavior would be incompatable with format's current behavior of outputting the state in 1-3 output variables according to nargout.

see https://www.mathworks.com/help/matlab/ref/format.html

some testing also shows that it permits simultaneous inputs and outputs, storing the previous setting in the output variable, then setting the new state:

>> a = format

a =

  DisplayFormatOptions with properties:

    NumericFormat: "short"
      LineSpacing: "loose"

>> a = format('longe')

a =

  DisplayFormatOptions with properties:

    NumericFormat: "short"
      LineSpacing: "loose"

>> a = format

a =

  DisplayFormatOptions with properties:

    NumericFormat: "longE"
      LineSpacing: "loose"