Consider the minimally reproducible example:

f = @(x) x
f(end)

Note, the MATLAB syntax highlighter doesn’t actually highlight end in blue, showing that it is not parsing as a keyword, even though the Stack Overflow syntax highlighting does.

Output:

f =

  function_handle with value:

    @(x)x


ans =

     1

You can even do things like

f = @(x) x
a = f(end + 1)
b = f(end - 100)
c = f(2 + end)

Output:

a =

     2


b =

   -99


c =

     3

Regular Function

If you have a regular function, this doesn’t work

foo(end)

function x = foo(x)
end

Error: <filename> Line: 1 Column: 5
The end operator must be used within an array index expression.

Hypothesis

From this, it appears that end is being coerced into the value 1, similar to how the boolean/logical true gets coerced to 1. My hypothesis is that since the function handle is actually a 1×1 array of function handles, the end keyword is replaced by the last valid index of the array which is 1. Since a function is not stored as an array, it doesn’t work for real functions.

My Bug

I had a particularly nasty bug where I was was trying to index into an array with a similar name as a function handle:

x = 1:5
foo = @(x) x
foos = foo(x) % [1, 2, 3, 4, 5]
out = foos(1) + 2 * sum(foos(2:end-1)) + foo(end)
% Expected: out = 1 + 2 * (2 + 3 + 4) + 5 = 24, Got: out = 1 + 2 * (2 + 3 + 4) + 1 = 20

Obviously, I renamed my variables to make them more distinguishable. Still, this behavior doesn’t seem useful for anything that I can think of. Is this an artifact of result of every object (including a function handle) secretly being an array? If so, is there anything the user do to prevent this or does a fix need to come from MathWorks?