title: Haskell: Not in scope: foldl'?
body: <p>As my first module experience, I imported Data.List to my GHCi. (More precisely, I typed <code>import Data.List</code> on my GHCi) It seems to be working fine because I can use some functions that I did not have before such as <code>foldl'</code> on my GHCi. </p>
  
  <p>I wrote <code>haha = foldl' (+) 0 [1..10]</code> on my notepad++, and saved it and loaded then GHCi says <code>Not in scope: foldl'</code> even though it workds just fine when I type <code>foldl' (+) 0 [1..10]</code> directly on my GHCi. </p>
  
  <p>Why is that and how can I define functions with <code>foldl'</code> on my notepad?</p>