Interpreting the strictness annotations output by ghc --show-iface

John Meacham john at
Thu Mar 8 02:04:55 CET 2012

On Wed, Mar 7, 2012 at 5:01 PM, Johan Tibell <johan.tibell at> wrote:
> On Wed, Mar 7, 2012 at 4:38 PM, Brandon Allbery <allbery.b at> wrote:
>> I think the original type signature is needed to figure it out.  In the
>> earlier example it indicated ghc drilling down into the type (a tuple) and
>> determining the strictness of the constituents.
> I parenthesis were for tuples I would never expect to see e.g. U(L).

They are for all CPR types, not just tuples. so that could be

data Foo = Foo Int

It also may omit values for which is has no information for, I can't
recall if ghc does that or not.


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