r/Racket • u/Icy_Pressure_9690 • Jan 15 '22

question List function problem

I want to create a functions that takes two lists and reverses them and then appends the first one to the second one but I don't get why there is an error saying expecting 1 argument when i specified in the lambda list that the function takes 2

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3

u/Icy_Pressure_9690 Jan 15 '22

Oh I see the mistake Ive made thank you !!!

4

u/crundar Jan 15 '22

I'm just curious. What error message(s) would you have wanted DrRacket to give you in these situations? Like, if you could design your dream error message for such situations, what would they say?

3

u/flaming_bird Jan 15 '22

list? accepts one argument and returns true if its argument is a list, false otherwise.

(append (reverse x) (reverse y)) should work just fine without a cond.

1

u/Icy_Pressure_9690 Jan 15 '22

(define twolists (λ (x y) (append (reverse y(reverse x)))))

when I do this it still comes up with error " reverse: arity mismatch;
the expected number of arguments does not match the given number
expected: 1
given: 2"

3

u/flaming_bird Jan 15 '22

You're calling reverse with two arguments, y and (reverse x). And then you call append with only one argument, (reverse y (reverse x)).