Language.Nix.Identifier

Documentation

Identifiers in Nix are essentially strings. They can be constructed (and viewed) with the ident isomorphism. For the sake of convenience, Identifiers are an instance of the IsString class.

Reasonable people restrict themselves to identifiers of the form [a-zA-Z_][a-zA-Z0-9_'-]*, because these don't need quoting. The methods of the Pretty class can be used to pretty-print an identifier with proper quoting:

>>> pPrint (ident # "test")
test
>>> pPrint (ident # "foo.bar")
"foo.bar"

data Identifier

Instances

Eq Identifier

Ord Identifier

Show Identifier

IsString Identifier

NFData Identifier

Pretty Identifier

An isomorphism that allows conversion of Identifier from/to the standard String type via review.

\str -> fromString str == ident # str

\str -> set ident str undefined == ident # str

\str -> view ident (review ident str) == str

ident :: Iso' Identifier String

Helper function to quote a given identifier string if necessary.

>>> putStrLn (quote "abc")
abc
>>> putStrLn (quote "abc.def")
"abc.def"

quote :: String -> String

Checks whether a given string needs quoting when interpreted as an Identifier.

needsQuoting :: String -> Bool