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As I was writing up an answer just now, I ran across an interesting problem: data Gender = Male | Female deriving (Eq, Show) data Age = Baby | Child | PreTeen | Adult deriving (Eq, Show, Ord) data Clothing = Pants Gender Age | Shirt Gender Age | Skirt Age -- assumed to be Female deriving (Show, Eq) Suppose I wish to write the final data type with record syntax: data Clothing = Pants {gender :: Gender, age :: Age} | Shirt {gender :: Gender, age :: Age} | Skirt {age :: Age} deriving (Show, Eq) The problem is, I want gender $ Skirt foo to always evaluate to Female (regardless of foo , which is an Age ). I can think of a few ways to accomplish this, but they require that I either use smart constructors, theoretically allowing Skirt Male foo but not exposing Constructors define my own gender function With #1, by not exposing the constructor in the module, I effectively prevent users of the module from taking advantage of record syntax. With #2, I have to forego record syntax entirely, or define an additional function gender' , which again defeats record syntax. Is there a way to both take advantage of record syntax, and also provide a "default", unchangeable value for one of my constructors? I am open to non-record-syntax solutions as well (lenses, perhaps?) as long as they are just as elegant (or moreso).

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