Commit 77a4675a authored by Ian Lynagh's avatar Ian Lynagh
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Update the docs on how you bind unlifted types in let/where clauses

parent 8bf9fcc6
......@@ -210,22 +210,20 @@ in a <emphasis>top-level</emphasis> binding.
in a <emphasis>recursive</emphasis> binding.
<listitem><para> You may bind unboxed variables in a (non-recursive,
non-top-level) pattern binding, but any such variable causes the entire
to become strict. For example:
non-top-level) pattern binding, but you must make any such pattern-match
strict. For example, rather than:
data Foo = Foo Int Int#
f x = let (Foo a b, w) = ..rhs.. in ..body..
Since <literal>b</literal> has type <literal>Int#</literal>, the entire pattern
is strict, and the program behaves as if you had written
you must write:
data Foo = Foo Int Int#
f x = case ..rhs.. of { (Foo a b, w) -> ..body.. }
f x = let !(Foo a b, w) = ..rhs.. in ..body..
since <literal>b</literal> has type <literal>Int#</literal>.
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