Given a file input.txt, which consists of a number of elements in arrays and elements in the arrays, I should read the data and copy it to arrays in Eiffel. For example, for

3 
3 4 5
2 3 1

I should get len = 3, a1 = {3,4,5}, a2 = {2,3,1}.

I have tried the following but it was not successful

take_input
        -- Read user's input.
    local
        input: PLAIN_TEXT_FILE
        output: PLAIN_TEXT_FILE
        itr: INTEGER
    do
        create input.make_open_read ("input.txt")
        input.read_integer
        len := input.last_integer
        create output.make_open_write ("output.txt")
        create num.make_filled (0, 1, len)
        create rem.make_filled (0, 1, len)
        from
            input.start
            input.read_integer
            itr := 0
        until
            input.off
        loop
            itr := itr + 1
            if itr <= len then
                num [itr] := input.last_integer
                input.read_integer
            else
                rem [itr - len] := input.last_integer
                input.read_integer
            end
        end
        input.close
    end

Here Is there any way I can continously read the inputs rather than again starting from the Begginning of the file?

How can a mail be sent in eiffel with kernel library? which class to use?

Which library of the kernel should I use to sort a collection in eiffel?

where can I find an example of sort? are the tipical bubble sort, etc available?

Any sorter with agent would be very useful too to avoid having to do it with a comparable which is not implemented for example with PATH class

As I'd like to know if some object is into a LINKED_SET to prune it in my context, I'm unable to compare it as an object instead of its reference.

changeable_comparison_criterion: BOOLEAN
        -- May `object_comparison' be changed?
        -- (Answer: only if set empty; otherwise insertions might
        -- introduce duplicates, destroying the set property.)
    do
        Result := is_empty
    ensure then
        only_on_empty: Result = is_empty
    end

Into the SET class (as above) it seems that its not possible to change a set to compare_objects. So my questions are:

1. What is the semantic of not being able to compare objects into a SET
2. If my choice of LINKED_SET is wrong by misunderstanding of its semantic, how should I do for having a unique items collection based on object comparison and then being able to prune an item again based on object comparison again