[REBOL] Re: Refinements

From: jan:skibinski:sympatico:ca at: 12-Nov-2002 14:03

    Hi Robert,
    I am sure there are many ways of approaching this task.
    Here is one:
    Provided are three functions: 'f1, 'f2 and refine.
    F2 is a worker, 'f1 is your caller and 'refine is
    a dispatching utility. Example:

    >> f1 "Robert"
    == "Robert is in the middle"
    >> f1/left "Robert"
    == "Robert is on the left"
    >> f1/right "Robert"
    == "Robert is on the right"

    Regards,
    Jan
    -------------------------------------------------------

   f1: func [
        x /left /right
        /local f
    ][

        either left [
            f: refine/left :f2
        ][
            either right [
                f: refine/right :f2
            ][
                f: refine :f2
            ]
        ]
        comment {
            Do what you need to do here and finally
            call your f2 with a preselected refinement}
        f x
    ]

    f2: func [
        x /left /right
    ][
        either left [
            rejoin ["" x " is on the left"]
        ][
            either right [
                rejoin ["" x " is on the right"]
            ][
                rejoin ["" x " is in the middle"]
            ]
        ]
    ]

    refine: func [
        {Select a refinement /left /right or none
        for a function 'f}
        f [any-function!] /left /right
        /local result
    ][
        pipe: func[fs][make function! [x] append copy fs 'x]
        either left [
            result: pipe [f/left]
        ][
            either right [
                result: pipe [f/right]
            ][
                result: pipe [f]
            ]
        ]
        :result
    ]

Robert M. Muench
 wrote:

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