If in one .m file, I write a nested function inside the main function, then I wonder if this nested function can call a function in another .m file?

I know that local functions cannot call exterior functions (i.e., functions in other .m files) but the main function can, however, what about the nested function?

Answer 1

[Walter Roberson]

Local functions and nested functions can call any reachable function, whether in the same .m or a different .m

The restriction is "reachable". Usually a local or nested function can only reach functions that are in the same .m or which are the first function in a .m file. However, if the local or nested function has access to a function handle to a buried function, then it can execute the function.

For example:

file file1.m

   function file1
     f1 = file2();
     function nested1
       f1(7);
     end
     nested1()
   end

file file2.m

function h = file2
  h = @local2;
function y = local2(x)
  y = x.^2 - 1;

Here, calling upon file2 returns a handle to the local function local2. Once that handle has been stored in f1, nested1 can use that handle to invoke local2 even though local2 would otherwise not be reachable from nested1 (because it is not the first function in its own .m file)