What do you get if u invoke a method with the wrong number of arguments ?? It throws in ur face ArgumentError … it doesn’t try to be polite, you are at fault since you are the one that breaches the contract !!

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def m0
  :ok
end

m0    # >> :ok
m0(1) # >> (...) wrong number of arguments (1 for 0) (ArgumentError)

It tells you that it is expecting 0 argument, yet you have passed it 1 argument. Let’s have another one:

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def m2(x, y)
  :ok
end

m2       # >> (...) wrong number of arguments (0 for 2) (ArgumentError)
m2(1)    # >> (...) wrong number of arguments (1 for 2) (ArgumentError)
m2(1, 2) # >> :ok

Pretty readable rite ?