function chaining when one function has multiple outputs
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Simon
on 19 Aug 2024 at 20:27
Commented: Simon
on 20 Aug 2024 at 17:20
Similar question has been asked before, but I would ask the question in a more specific manner. If the function in the input end has more than one output, there will be the error 'Not enough input arguments'. Is there a neat way to make chained function out of that situation?
f(g) % only the first output of g is kept as input for f
function [x, y] = g()
x = 1;
y = 2;
end
function out = f(x, y)
out = x+y;
end
Storing the outputs of the first function in two variables could be a solution, but I like to see how chaining could be done in this kind of scenario for the sake of learning.
[x, y] = g();
f(x, y)
2 Comments
Stephen23
on 20 Aug 2024 at 5:24
Edited: Stephen23
on 20 Aug 2024 at 5:58
"Is there a neat way to make chained function out of that situation? "
No. The MATLAB apporoach is to call the two functions on two lines: this works because MATLAB's function outputs are demand driven. A discussion of why this behavior is required:
Accepted Answer
Steven Lord
on 19 Aug 2024 at 20:48
Suppose you had a function that could be called with either 1 output or more outputs, and a function that can accept 1 input or multiple inputs. If you chained those two so that the output(s) of the first of those functions were passed into the second function, how should MATLAB know with how many outputs to call the first function? To give an example (not necessarily a realistic example but just to illustrate the situation):
A = magic(4);
L = lu(A);
oneOutputCase = max(L)
[L, U] = lu(A);
twoOutputCase = max(L, U)
chainCase = max(lu(A))
Were you expecting the twoOutputCase output from the chainCase call? The lu function can return up to five outputs (though the fourth and fifth are only supported for sparse inputs, but the first three are supported for both sparse and full inputs) and the max function can accept (as data inputs) one or two inputs. How would you expect MATLAB to distinguish between those two cases?
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