Re: [Haskell-cafe] instance of String illegal

On 29/09/2006, at 12:44 PM, Donald Bruce Stewart wrote:

Alternatively, use -fglasgow-exts :)

...

instance Foo String where mkFoo = id

$ ghci -fglasgow-exts A.hs *Main> mkFoo "foo" "foo"

And just to follow up what Don said, this feature of GHC is described here: http://www.haskell.org/ghc/docs/latest/html/users_guide/type- extensions.html