Stupid MATLAB Tricks.

stupid_tricks.matlab

function stupid_tricks

    % I made some functional tools for MATLAB.
    assert(reduce_(@(x, y) x + y, [1, 2, 3, 4]) == 10)

    % They got a little out of hand.
    join = @(sep, args) ...
        if_(ischar(sep), @() ... % Input check
            reduce_(@(x, y) [x sep y], ... % Reduce to string
                map_(@num2str, args))); % Convert args to string.

    assert(strcmp(join(', ', {1, 2, 3, 4}), '1, 2, 3, 4'));

    % And then they just got ridiculous.
    tail = @(lst) lst(2:end);
    head = @(lst) lst(1);
    
    qs = Y(@(self) @(lst) ...
             if_(isempty(lst), ...
               @() [], ... # Is empty
               @() [...
                self(tail(lst(lst <= head(lst))))
                head(lst)
                self(lst(lst > head(lst)))]));
            
    assert(all(qs([8,2,45,0,4,1,2,3]) == [0, 1, 2, 2, 3, 4, 8, 45]'));
end

%%%%%%%%% Functions %%%%%%%%%%%%%%%

function retval = apply(fn, args)
    if isnumeric(args)
        args = num2cell(args);
    end

    retval = fn(args{:});
end

function retval = map_(fn, args)
    was_numeric = isnumeric(args);
    if was_numeric
        args = num2cell(args);
    end

    retval = cellfun(fn, args, 'UniformOutput', false);

end

function retval = reduce_(fn, vals, varargin)
    if ~iscell(vals)
        vals = num2cell(vals);
    end

    if nargin > 2
        retval = varargin{1};
        start = 1;
    else
        retval = fn(vals{1}, vals{2});
        start = 3;
    end

    for ii=start:length(vals)
        retval = fn(retval, vals{ii});
    end
end

function retval = if_(predicate, if_fn, else_fn)
    if predicate
        retval = if_fn();
    else
        retval = else_fn();
    end
end

function res = Y(f)
    res = apply(...
        @(x) f(@(y) apply(apply(x, {x}), {y})), ...
        {@(x) f(@(y) apply(apply(x, {x}), {y}))});
end