CODEWITHSUNDEEP
matlabparsinginputoctave
babelproofreader
babelproofreader

Reputation: 552

Problem with validateattributes function in Octave

I am trying to port some MATLAB code from GitHub to Octave and having problems with parsing the function input. There is/are optional input parameters which are handled thus:

% Optional parameter: maxLag
defaultMaxLag = 10 ;
checkMaxLag = @(x) validateattributes( x , { 'numeric' } , { 'positive' , 'numel' , 1 } ) ;

which are then handled by the inputParser:

addOptional( parser , 'maxLag' , defaultMaxLag , checkMaxLag ) ;

If I try running this code as is I get the error

error: mdDelay: argument 'MAXLAG' is not a valid parameter

My Octave translation of this last code snippet is

addParamValue( parser , 'maxLag' , defaultMaxLag , checkMaxLag ) ;

which is also failing, but with the error message

error: if: undefined value used in conditional expression
error: called from
validate_arg at line 521 column 9
parse at line 470 column 11

The problem seems to be the anonymous function checkMaxLag because when I run just this in the terminal I get

error: value on right hand side of assignment is undefined

so it seems that validateattributes does not give a return value that the inputParser requires. Any suggestions?

Upvotes: 0

Views: 704

Answers (1)

carandraug
carandraug

Reputation: 13091

Your problem has nothing to with the change from addOptional to addparamValue to the port. The problem is simply that this fails (the error message recently on a newer version):

octave> validate_lag = @(x) validateattributes (x, {'numeric'}, {'positive', 'numel', 1});
octave> p = inputParser ();
octave> p.addOptional ('maxLag', 10, validate_lag);
octave> p.parse (20)
error: failed validation of MAXLAG
Validation function: @(x) validateattributes (x, {'numeric'}, {'positive', 'numel', 1})

You got caught by Octave's bug #49793. Basically, inputParser expects a validation function that returns true or false. However, validateattributes either returns nothing or fails. I recommend you do this:

function rv = validateattributes_with_return_value (varargin)
  try
    validateattributes (varargin{:});
    rv = true;
  catch
    rv = false;
  end_try_catch
endfunction

And then you can use

validate_lag = @(x) validateattributes_with_return_value (x, {'numeric'}, {'positive', 'numel', 1});

Upvotes: 3

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