CODEWITHSUNDEEP
clojure
sebhs
sebhs

Reputation: 143

Calling a function within conj in clojure

I'm a newbie to Clojure and am a bit confused about how functions are called.

Let's say I have this function

(defn  foo [& fns] 
   #(apply (first fns) %&))

When I call ((foo + max min) 2 3 5 1 6 4) it will return 21.

When I define the function like this, 

(defn  foo [& fns] 
   (conj [] #(apply (first fns) %&)))

I was expecting ((foo + max min) 2 3 5 1 6 4) to return [21] but instead I get 

Execution error (ArityException) at user/eval2258 (REPL:1).
Wrong number of args (6) passed to: clojure.lang.PersistentVector

Why is that? And how would I fix it?

Upvotes: 0

Views: 67

Answers (1)

cfrick
cfrick

Reputation: 37073

(defn  foo [& fns] 
   (conj [] #(apply (first fns) %&)))

I was expecting ((foo + max min) 2 3 5 1 6 4) to return [21]...

Your original foo returns a function. Now you return a vector with a function in it. Now when calling it, you are calling the vector, thus the error message.

user=> ([] 1 2 3)
Execution error (ArityException) at user/eval150 (REPL:1).
Wrong number of args (3) passed to: clojure.lang.PersistentVector

To correct this, you would have put the result of the apply into the vector, but still return a function. But since you are not yet using all passed in fns it's not clear, what to suggest from here.

This would give you the result, you are looking for:

(defn  foo [& fns] 
   #(vector (apply (first fns) %&)))

Upvotes: 4

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