Externalise functions into a library

Hello

In brief, what you're trying to do would be accomplished by setting parent of library script object to the caller script which loads the library at run-time.

Here's silly scripts just to demonstrate the concepts. The lib.scpt is the complied script of library saved on desktop. The template.applescript is the template of caller. Note that lib.scpt consists of constructor which is to set the parent property of lib script object at run-time and caller (template) calls the constructor with the parent argument set to self. This construct will realise the features requested in Q2, Q4 and Q5. As for Q4 & Q5, you'd need to resort to something like exists_handler() and exists_reference() in lib.scpt because AppleScript language itself does not provide introspection facilities.

--lib.scpt
on new_lib(pobj)
    script lib
        property parent : pobj
        property p1 : 1 * minutes -- unit 1
        property p2 : 1 * hours -- unit 2
        property p3 : missing value -- base date
        
        on exists_handler(h)
            try
                return h's class = handler
            on error number -1700
                return false
            end try
        end exists_handler
        
        on exists_reference(s)
            try
                s's contents
                return true
            on error number -1700
                return false
            end try
        end exists_reference
        
        on init()
            -- validation of parent's handlers and properties
            set chk1 to exists_handler(a reference to parent's getLiveData)
            set chk2 to ¬
                exists_reference(a reference to parent's q1) and ¬
                exists_reference(a reference to parent's q2)
            
            if not chk1 then error "some handler missing" number 8000
            if not chk2 then error "some property missing" number 8001
            
            -- get live data from parent
            set p3 to my getLiveData()
        end init
        
        on main()
            --
        end main
        
        on f1(x)
            (*
                number x : shift amount
                return string : string representation of a date (= my q1 ? p3 + x * p1 : p3 + x * p2)
            *)
            if my q1 then
                return f2(p3 + x * p1)
            else
                return f2(p3 + x * p2)
            end if
        end f1
        
        on f2(x)
            (*
                date x : source date
                return string : string representation of x
                    my q2 ? localised string : iso string
            *)
            if my q2 then
                x as string
            else
                x as «class isot» as string
            end if
        end f2
    end script
end new_lib
--end of lib.scpt

--template.applescript
property lib : missing value
property q1 : true -- unit = minute or hour
property q2 : false -- output format = localised date or iso date

on getLiveData() -- to be invoked by lib
    return current date
end getLiveData

on init()
    -- create and initialize a instance of lib with its parent set to self
    set lib to new_lib(me) of (load script POSIX file ((path to desktop)'s POSIX path & "lib.scpt"))
    lib's init()
end init

on main()
    tell lib
        -- modify properties in lib
        set {its p1, its p2} to {(its p1) * 2, (its p2) * 2}
    end tell
    -- retrieve property and invoke handler in lib
    return {lib's p3, lib's f1(5)}
end main

init()
main()
--end of template.applescript

As for Q3, it depends. In my opinion, the simpler, the better. AppleScript is not designed for large-scale libraries. It's rather involved if not impossible to implement multiple inclusions and manage dependencies. By the way, I don't understand the use of main() in lib.scpt because it is supposed to be a collection of handlers. So I did not implement it in the sample codes listed above.

As for Q1, AppleScript Language Guide is the primary document you must peruse. Especially the chapters "Variables and Properties" and "Script Objects".

https://developer.apple.com/library/mac/documentation/AppleScript/Conceptual/App leScriptLangGuide/

https://developer.apple.com/library/mac/documentation/AppleScript/Conceptual/App leScriptLangGuide/AppleScriptLanguageGuide.pdf

Also you might find the following old thread of some use. There I've written an afterword for reference.

tell/scoping problem

https://discussions.apple.com/thread/2477010?start=0&tstart=0

Re: re: my parent

https://discussions.apple.com/thread/2477010?answerId=11852193022#11852193022

Hope this may help,

H