[Haskell-beginners] "stage restriction" when using Data.Heap

[Twan van Laarhoven]

On 08/01/13 07:03, Martin Drautzburg wrote:
> import Data.Heap
>
> heap = empty :: MinHeap (Int,String)
> insert (1,"kjh") heap

Your error is in the last line. `insert (1,"kjh") heap` is an expression, and in 
Haskell expressions can only occur inside (function) declarations. So you should 
instead write something like:

     heap = empty :: MinHeap (Int,String)
     heap2 = insert (1,"kjh") heap

In Ghci, expressions are evaluated and the result is printed, which is why you 
are able to use it there.


Twan