Create function output seperately

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Kristoffer Lindvall 2018-9-11

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https://ww2.mathworks.cn/matlabcentral/answers/418458-create-function-output-seperately

评论： Guillaume 2018-9-11

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Hello!

I am curious if this is possible. Say I write a function

function F = func(x)
   F(1) = x(1)-cos(x(2));
   F(2) = x(2)-cos(x(1));
end

Now every time I call on this function it calculates the RHS of the equation and gives an output for F. Now if I had a ton of calculations before F that I don't want Matlab to constantly repeat, all I want is the last statement F.

An example would be

function F = func(x)
   % I send the x vector in order to get boundary conditions
   BC = Boundaries(x);
   % Now BC is a function with equations like BC(1) =  x(1)+x(2)... etc
   F(1) = BC(1);
   F(2) = BC(2);
end

I want to use the function F(1) = x(1)+x(2), and not have to constantly send x to BC to "create" those equations.

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Stephen23 2018-9-11

编辑：Stephen23 2018-9-11

Then why not just move Boundaries outside of func and calculate it only once?

Guillaume 2018-9-11

Still not entirely clear on what is being asked, not helped by the imprecise terms used. You don't make functions. Functions don't create equations. You call a function with some inputs and it returns some outputs.

In addition to what has already been suggested, since R2017a, there is also the possibility of memoizing a function, a technique that caches the results of a function that is expensive to run so that it is only run if different inputs are provided. No idea, if that's what you're after.

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