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Monday, November 9, 2009

Remembering Function Definitions


OK I know this is both paternalistic and heterocentric. However, if you need a good way to demonstrate Function, 1:1, and Onto, "A School Dance" gets the job done.

I give them a sheet with these slides and ask them to conjecture about the definitions.






7 comments:

  1. I'm more worried about students making inappropriate comments about "onto".

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  2. Hi Kate,

    Does the first slide actually count as a function? I'm worried about the little blue stick figure in the top left corner -- he doesn't get assigned to anybody. Does that mean he's not in the "School Dance" domain?

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  3. @Regular it depends who you ask. Computer science people don't require a relation to cover every element of the domain to be a function, and they speak of "partial" and "total" functions.

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  4. Yep. Lonely dude is a problem. I suck.

    Here is what my dark overlords in Albany say:

    function : A rule that assigns to each number x in the function's domain a unique number f(x).

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  5. but dammit a function is a set of ordered pairs.

    and if numbers had anything to do with it
    the the kids at the dance don't qualify.

    unapolgetic made a related point in my blog
    yesterday.

    computerheads are of course wrong.
    all functions are total functions.
    i'm just a bigot that way.

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  6. anyhow your overlords are on shaky ground
    philosophically because of the recursive nature
    of their definition. to know what a function is,
    one evidently has to know what "the function" is.
    gnu's not unix! turtles all the way down! repent!

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  7. They're the mayor of shaky philosophical ground.

    ReplyDelete

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