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@lrq3000 lrq3000/getnargs.m
Last active Aug 29, 2015

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GETNARGS an Octave/MatLab function to use named optional arguments
function argStruct = getnargs(varargin, defaults, restrict_flag)
%GETNARGS Converts name/value pairs to a struct (this allows to process named optional arguments).
% ARGSTRUCT = GETNARGS(VARARGIN, DEFAULTS, restrict_flag) converts
% name/value pairs to a struct, with defaults. The function expects an
% even number of arguments in VARARGIN, alternating NAME then VALUE.
% (Each NAME should be a valid variable name and is case sensitive.)
% Also VARARGIN should be a cell, and defaults should be a struct().
% Optionally: you can set restrict_flag to true if you want that only arguments names specified in defaults be allowed. Also, if restrict_flag = 2, arguments that aren't in the defaults will just be ignored.
% After calling this function, you can access your arguments using: argstruct.your_argument_name
% Examples:
% No defaults
% getnargs( {'foo', 123, 'bar', 'qwerty'} )
% With defaults
% getnargs( {'foo', 123, 'bar', 'qwerty'} , ...
% struct('foo', 987, 'bar', magic(3)) )
% See also: inputParser
% Authors: Jonas, Richie Cotton and LRQ3000
% Extract the arguments if it's inside a sub-struct (happens on Octave), because anyway it's impossible that the number of argument be 1 (you need at least a couple, thus two)
if (numel(varargin) == 1)
varargin = varargin{:};
% Sanity check: we need a multiple of couples, if we get an odd number of arguments then that's wrong (probably missing a value somewhere)
nArgs = length(varargin);
if rem(nArgs, 2) ~= 0
error('NameValuePairToStruct:NotNameValuePairs', ...
'Inputs were not name/value pairs');
% Sanity check: if defaults is not supplied, it's by default an empty struct
if ~exist('defaults', 'var')
defaults = struct;
if ~exist('restrict_flag', 'var')
restrict_flag = false;
% Syntactic sugar: if defaults is also a cell instead of a struct, we convert it on-the-fly
if iscell(defaults)
defaults = struct(defaults{:});
optionNames = fieldnames(defaults); % extract all default arguments names (useful for restrict_flag)
argStruct = defaults; % copy over the defaults: by default, all arguments will have the default value.After we will simply overwrite the defaults with the user specified values.
for i = 1:2:nArgs % iterate over couples of argument/value
varname = varargin{i}; % make case insensitive
% check that the supplied name is a valid variable identifier (it does not check if the variable is allowed/declared in defaults, just that it's a possible variable name!)
if ~isvarname(varname)
error('NameValuePairToStruct:InvalidName', ...
'A variable name was not valid: %s position %i', varname, i);
% if options are restricted, check that the argument's name exists in the supplied defaults, else we throw an error. With this we can allow only a restricted range of arguments by specifying in the defaults.
elseif restrict_flag && ~isempty(defaults) && ~any(strmatch(varname, optionNames))
if restrict_flag ~= 2 % restrict_flag = 2 means that we just ignore this argument, else we show an error
error('%s is not a recognized argument name', varname);
% else alright, we replace the default value for this argument with the user supplied one (or we create the variable if it wasn't in the defaults and there's no restrict_flag)
argStruct = setfield(argStruct, varname, varargin{i + 1}); %#ok<SFLD>
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