Re: Constants in functions?

[Sergei Steshenko]

On 05/03/2020 20:12, Windhorn, Allen E [ACIM/LSA/MKT] wrote:
> What's the accepted way to define a constant inside a function?  Example:
> ____________________________________
> function [sc, err] = symmcomp(abc)
>    % Function accepts [abc] complex components and delivers symmetrical
>    % components as a vector [x0, x1, x2] of complex values
>    persistent a = complex(-0.5, sqrt(3)/2);    % Rotation vector
>    %
>    % Build conversion matrix_type (constant)
>    persistent A = [1, 1, 1;
>                 1, a, a^2;
>                 1, a^2, a]./3;
>    %
>    % Make abc a column vector
>    if (length(abc)>3)
>      sc = [];
>      err = "Too many components!";
>    elseif (length(abc)<3)
>      sc = [];
>      err = "Too few components!";
>    else
>      abc = reshape(abc,[3,1]);
>      sc = A*abc;
>      err = "";
>    endif
> endfunction
> ________________________________________
>
> Here a is a constant and A is a constant matrix.  I used persistent in hopes
> it would prevent them from being redefined every time the function is called.
> In C++ I would use the "const" keyword.
>
> Regards,
> Allen


An ugly (because IIRC Octave doesn't have nested functions) way:

function retval = TWO()

  retval = 2;

endfunction

.

The above function will return 2. You can similarly return matrix, row o 
column vector, etc.


--Sergei.