update for rename of topics/closures.mdwn to topics/week7__95__environments__95__and_...

[lambda.git] / exercises / assignment5.mdwn

diff --git a/exercises/assignment5.mdwn b/exercises/assignment5.mdwn
index 7388948..5dd1cbb 100644 (file)
--- a/exercises/assignment5.mdwn
+++ b/exercises/assignment5.mdwn
@@ -252,6 +252,8 @@ Again, we've left some gaps. (The use of `type` for the first line in Haskell an
 
 15. Choose one of these languages and fill in the gaps to complete the definition.
 
 
 15. Choose one of these languages and fill in the gaps to complete the definition.
 

+<a id="occurs_free"></a>
+

 16. Write a function `occurs_free` that has the following type:
 
         occurs_free : identifier -> lambda_term -> bool
 16. Write a function `occurs_free` that has the following type:
 
         occurs_free : identifier -> lambda_term -> bool


@@ -329,7 +331,9 @@ any type `α`, as long as your function is of type `α -> α` and you have a bas
         -- Or this:
         let sysf_true = (\y n -> y) :: Sysf_bool a
 
         -- Or this:
         let sysf_true = (\y n -> y) :: Sysf_bool a
 

-            :set -XExplicitForAll
+    Note that in both OCaml and Haskell code, the generalization `∀α` on the free type variable `α` is implicit. If you really want to, you can supply it explicitly in Haskell by saying:
+
+        :set -XExplicitForAll

         let { sysf_true :: forall a. Sysf_bool a; ... }
         -- or
         let { sysf_true :: forall a. a -> a -> a; ... }
         let { sysf_true :: forall a. Sysf_bool a; ... }
         -- or
         let { sysf_true :: forall a. a -> a -> a; ... }