Save several results from recursive function

Question

BYQQY 2021-4-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/817460-save-several-results-from-recursive-function

评论： BYQQY 2021-5-1

I have written some code that that takes a textfile and applies the huffman algorithm and constructs a "Huffman tree" using nested cell arrays.

Basically I have my cell array G which of size 1x2, in turn containing 1x2 cell arrays and so on until it reach the end element which is of class char.

For example G{1}{1}{1}{1}{1}{1} = 'h' which tells me that the codeword for h is 00000 (G{1} is the root).

Now I want to parse my cell array G so I can process the data easier. Basically I want to put my data in another cell array or table like

x y

char1 codeword1

char2 codeword 2

and so on...

For this I have a recursive function

function y = parsecell(c,s)
if nargin==1
    s = inputname(1);
end
for i=1:numel(c)
  if iscell(c{i}) && ~isempty(c{i})
    parsecell(c{i},[s subs(i,size(c))])
  else
    disp([s(3:end) subs(i,size(c)) ' = ' c{i}])
  end
end
end

which gives me outputs like

0 0 0 0 0 = h.

for every end element in G.

I'm struggling with somehow creating my new cell array or table. For example I was thinking that I could replace disp() with something like

y{end+1,1} = [s(3:end) subs(i,size(c)) ' = ' c{i}];

but I can't get it to work.

Any help is appreciated!

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Walter Roberson 2021-4-30

You are passing the numeric value of i as the first parameter of subs() but the first parameter must be a symbolic function or symbolic expression, unless you have a sufficiently old version of MATLAB in which case a character vector was also a possibility.

BYQQY 2021-5-1

I'm not really sure what you mean here. But I'm not having any problem with (I think?) with subs().

For example if I try

x={};
parsecell(G,x)
function  parsecell(c,x,s)
if nargin==2
    s = inputname(1);
end
for i=1:numel(c)
  if iscell(c{i}) && ~isempty(c{i})
    parsecell(c{i}, x,[s subs(i,size(c))])
  else
     x{end+1,1} = [s(3:end) subs(i,size(c))];
     x{end,2} =  c{i};
  end
end
end

it sort of works. But sometimes when

parsecell(c{i}, x,[s subs(i,size(c))])

is called x resets to an empty cell array and I don't know why

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Answer 1

Stephen23 2021-5-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/817460-save-several-results-from-recursive-function#answer_689300

In my experience by far the easiest way to achieve this is to use a nested function, something like (pseudocode):

function out = mymain(s);
out = {};
mynest(s)
    function mynest(t)
    if whatever checks you want
        out{end+1} = whatever
        mynest(t(2:end)) % recursive call
    end
    end
end