Wrong number of arguments

call.arity

Message

<function> expects N arguments, got M.

What it means

A call passes a different number of arguments than the function's signature or its indexed definition takes.

Why it happens

The signature (: f (-> A B C)) declares two parameters, but the call (f 1) passes one.

How to fix it

Pass the declared number of arguments, or update the signature and definitions if the arity changed.

(: add (-> Number Number Number))
(add 1)        ; call.arity: expects 2, got 1

Controlled by the metta.diagnostics.arity setting.