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:
I'm more worried about students making inappropriate comments about "onto".
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?
@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.
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).
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.
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!
They're the mayor of shaky philosophical ground.
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