Permits assignment to occur conditionally within a `a?.b` or `a?[b]` expression. // M() is only executed if 'a' is non-null. // note: the value of 'a.b' doesn't affect whether things are evaluated ...

# First up, on line 14, our hapless programmer has decided to check whether prime_array has a # value by using the .nil? method, which returns true if a value is nil and false otherwise. # This isn't ...