N/A exception is useful for specifying non-argument defaults when
nil
is a valid value.
def f(x=NA) end
NA is also used to represent an argument “slot” for Proc#partial.
NA is an instance of ArgumentError.
# File lib/core/facets/na.rb, line 12 def inspect ; 'N/A' ; end
# File lib/core/facets/na.rb, line 13 def method_missing(*); self; end