Write function with multiple output, like sort()
显示 更早的评论
B = sort(A);
[B, I] = sort(A);
How can I write such a function? Is it as simple as return both B and I, but the first line just uses B and ignore I, or there's some polymorphism trick under the hood?
采纳的回答
Tommy
2020-4-28
function [out1, out2, out3] = myfunc
...
end
As an example, this function has 3 outputs. You can call it with
[a, b, c] = myfunc
if you want, or you can use
a = myfunc
to just get out1, or perhaps
[~, b, c] = myfunc
to just get out2 and out3. Inside myfunc, each output simply needs to be assigned a value before the end of the function. Is this what you mean?
5 个评论
Rik
2020-4-28
It can:
function [a,I] = sort(A)
% bla bla
if nargout>1
%also compute I
end
end
Tommy
2020-4-28
Ah I see. If you tried to have both within the same file, you would get an error
'Function with duplicate name "sort" cannot be defined.'
and if they were in separate files, then MATLAB would just find the closest one and ignore the other one.
In MATLAB, it is up to whoever invokes a function to control which output variables are assigned, and that is where the flexibility lies. If you have some function
function [a, I] = sort(A)
% bla bla, but also compute I
end
you can't force whoever invokes it to request both outputs. It is valid for someone to call this function with just one output argument (which is wonderful). Therefore, if you also have the function
function a = sort(A)
% bla bla
end
and you call
b = sort(A)
how should MATLAB know which sort you are trying to call? MATLAB instead decides on its own, based solely on where the functions are located, and you'd better use syntax which is compatible with the one that MATLAB decides to go with.
Steven Lord
2020-4-28
You can't force someone to call your function with the desired number of outputs, but you could encourage then to do so or refuse to cooperate if they don't.
function [B, I] = mysort(A)
if nargout < 2
warning('You really should call mysort with two output arguments')
% or
error('You must call mysort with two output arguments')
end
% Do stuff to compute B and I
end
Tommy
2020-4-29
That's a good point!
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Data Type Identification 的更多信息
产品
Translated by 
