variable inputs function and reiteration

Hi everyone, Is there a way to write a function with variable input and reiterated computations? for example, I have to write this function:

 function[M] = fx(a1, a2, b1, b2, c1, c2, ....)
a=f(a1,a2);
b=f(b1,b2);
c=...
...
...
M=[a b c d ...];

Where f() is a generic function that I want to apply to every couple of input, and the number of these input is variable.

Answer 1

[Guillaume]

Use varargin.

function M = fx(varargin)
  if mod(nargin, 2) == 1
     error("you must supply an even number of arguments")
  end
  M = [varargin{1:2:end}] .* [varargin{2:2:end}];
end

[raffaele]

Sorry, I've explained not well the problem: I don't want to multiply x1*x2, I just want to apply a generic function to all the couple x1, x2. So I wondered if there is a way to say matlab to repeat the function that I apply to the input couple. I will give you an example: a=corr(a1, a2); b=corr(b1, b2); ... ... M=[a b ...]

[Guillaume]

It's still the same principle. This time you have to use a loop.

function M = fx(fn, varargin)
   if mod(nargin, 2) == 1
      error("you must supply an even number of arguments")
   end
   numpairs = numel(varargin) / 2;
   M = zeros(1, numpairs);
   for pair = 1:numpairs
      M(pair) = fn(varargin{pair*2-1}, varargin{pair*2});
   end
end

The bits between %% can be replaced by an arrayfun:

   M = arrayfun(@(pair) fn(varargin{pair*2-1}, varargin{pair*2}), 1:numel(varargin)/2);