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    • A completely different RPN solution.

    Posted by rlpowell on Sat 07 of Feb, 2009 20:53 GMT posts: 14214

    Just sending this because I haven't actually put it anywhere yet.

    -Robin

    --- Forwarded message from Robin Lee Powell <rlpowell@digitalkingdom.org> ---

    Subject: Palm Writings + RPN
    From: Robin Lee Powell <rlpowell@digitalkingdom.org>
    To: rlpowell@digitalkingdom.org
    Date: Tue, 28 Oct 2008 18:17:34 -0700


    Dammit, I'm too scared to put it on the Palm when I can't sync, so:

    @h1 A Completely Different RPN Solution

    We could have explicit push and pop operators in KOhA. Call them
    xa'a and xu'u, respectively. Usage would be like so:

    xa'a li pa sumji li re .i sumji li vo xu'u

    The first bridi adds 1 and 2 and pushes the result onto the stack.
    The second adds 4 to the topmost stack element.

    Given that, there could also be an RPN marker that would allow
    dropping the explicit push and pop, given text such as:

    li pa li re te sumji .i li vo li mu te sumji .i te pilji

    Determining where the implicit pops and pushes go doesn't even need
    to be semantic; it can be as simple as "How many places are free?
    If 1, push. If w e have N-1 on the stack, pull them in order, push
    the last. If we have less than that, error."

    With the occasional special case like a print bridi, which pulls
    exactly one and pushes none.

    For the implicit version, you probably want 2-argument sumji and
    pilji. You can use the explicit version with the inf-arg ones
    though.

    12:34 < Eimi> This is starting to sound like the hammer I need for
    my prenex nail. {le mi mlatu goi -push zo'u mi terpa tu'a -pop}

    -Robin

    --
    They say: "The first AIs will be built by the military as weapons."
    And I'm thinking: "Does it even occur to you to try for something
    other than the default outcome?" — http://shorl.com/tydruhedufogre
    http://www.digitalkingdom.org/~rlpowell/ *** http://www.lojban.org/

    --- End forwarded message ---

    --
    They say: "The first AIs will be built by the military as weapons."
    And I'm thinking: "Does it even occur to you to try for something
    other than the default outcome?" — http://shorl.com/tydruhedufogre
    http://www.digitalkingdom.org/~rlpowell/ *** http://www.lojban.org/


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    Posted by Jim Carter on Tue 10 of Feb, 2009 22:00 GMT

    On Sat, 7 Feb 2009, Robin Lee Powell wrote:

    > Subject: Palm Writings + RPN
    > From: Robin Lee Powell <rlpowell@digitalkingdom.org>
    > To: rlpowell@digitalkingdom.org
    > Date: Tue, 28 Oct 2008 18:17:34 -0700
    >
    > @h1 A Completely Different RPN Solution
    >
    > We could have explicit push and pop operators in KOhA. Call them
    > xa'a and xu'u, respectively. Usage would be like so:
    >
    > xa'a li pa sumji li re .i sumji li vo xu'u
    >
    > The first bridi adds 1 and 2 and pushes the result onto the stack.
    > The second adds 4 to the topmost stack element.
    >
    > Given that, there could also be an RPN marker that would allow
    > dropping the explicit push and pop, given text such as:
    >
    > li pa li re te sumji .i li vo li mu te sumji .i te pilji

    (etc.)

    This brings back fond memories. The mathematical expression syntax in Old
    Loglan was rather horrendous, and I was not satisfied with the grammar for
    simple dimensioned quantitites such as "I am 1.73 meters high". When I
    worked on gua\spi I took the opportunity to define mathematical expressions
    as RPN. This document section begins with math expressions (and continues
    with quantification, and sentence forms, which are not today's topic).
    http://www.math.ucla.edu/~jimc/guaspi/vocab2.html

    In "real" RPN no explicit stack pushing and popping are needed because the
    operators have a predetermined number of arguments; they always pop all
    their arguments and then push the single result. But if an operator had
    multiple results (e.g. quotient and remainder), or where you want to
    optimize a computation by computing a sub-expression once and then
    replicating the result, then explicit stack manipulation is needed.


    James F. Carter Voice 310 825 2897 FAX 310 206 6673
    UCLA-Mathnet; 6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA 90095-1555
    Email: jimc@math.ucla.edu http://www.math.ucla.edu/~jimc (q.v. for PGP key)


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