Re: Check if the environment is Octave or Matlab

[Colin Macdonald]

On 2020-04-10 12:21 p.m., Mike Miller wrote:
> As the manual shows, if you are assigning a variable anyway, avoid the
> if-else:
>
>      octave = (exist('OCTAVE_VERSION', 'builtin') == 5);
>
> and as others have suggested, you could make that persistent and/or
> global, depending on your needs.

We did some tests in the doctest project and decided that caching in a 
persistent variable wasn't worth it.  Here's our function, which has 
some timing info in the docstring:


function r = is_octave()
%IS_OCTAVE  True if we are running Octave, false for Matlab.

%%
% Copyright (c) 2015 Colin B. Macdonald
% SPDX-License-Identifier: BSD-3-Clause


% Timings for different implementations, 10000 calls
%
%     test        Matlab    Octave
%     ----------------------------
%     try-catch   1.2s      0.18s
%     if-exist    0.14s     0.22s
%     dummy       0.13s     0.13s
%
% Conclusions: "if-exist" only twice as slow as "dummy" (always return
% true), so no need to bother with a persistent variable.

  r = exist('OCTAVE_VERSION', 'builtin') ~= 0;

  %try
  %  OCTAVE_VERSION;
  %  r = true;
  %catch
  %  r = false;
  %end

end