In ruby, is truthiness idiomatic for a method name ending with a question mark?

Question

Is it normal for methods with a question mark to return something that\'s truthy (for example, a number) to indicate that something is true, or should true itself b

Answer 1

It is usual for methods ending with ? to return either true or false but it is not systematic and no core method will assume it.

An example in the core classes is Numeric#nonzero? which never returns true or false.

42.nonzero? # => 42

The library Set has add? and delete? too. I wish Enumerable#one? returned nil or false to distinguish cases where the count is zero from when it is greater than one.

A similar example are the comparison operators (<, >, ...), which usually return only true or false. Here again exceptions exist for Module's operators that will return nil instead when the two modules are not related:

Array > Enumerable  # => false
Array > Fixnum      # => nil