Reactive: running sunset reactor

[Reetu Singh]

I am running the sunset reactor.  When I hit run, everything looks "shipshape" when I type in interact (sunset-react) 

I get the following message 

An application errored.

1 argument was passed to the operator.

The operator evaluated to a function defined to accept 2 parameters:

definitions://:21:0-23:3

22

fun draw-state(a-SunsetState-x-value, a-SunsetState-y-value) :

23

  put-image(ground, 300, 10, (put-image(sun, a-SunsetState-x-value, a-SunsetState-y-value, sky)))

24

end 

An application expects the number of parameters and arguments to be the same.

(Show program evaluation trace...)

I don't know what this is referring to especially about the parameters and the arguments being the same.

Thank you!

[Joe Gibbs Politz]

Thanks for your message Reetu, it’s a good question.

One of the key phrases in Unit 3, which introduces draw-state, is

“The second step in making an animation is to write a function that consumes an instance of one state and produces the image for that instance.”

Based on this description, what should the *contract* of draw-state be? I’m focusing in particular on the part of the description that says “consumes *an instance*” of one state. This is a place where the contract, purpose statement, and examples of the draw-state function could help us understand what the rest of the program is expecting of draw-state.

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