<div dir="ltr"><div>You're missing the parens around (x:yx) in the last clause.<br></div></div><br><div class="gmail_quote">On Tue, 12 May 2015 at 11:02 Roelof Wobben <<a href="mailto:r.wobben@home.nl">r.wobben@home.nl</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
  

    
  
  <div bgcolor="#FFFFFF" text="#000000">
    Hello, <br>
    <br>
    I try to re implement ++ <br>
    <br>
    So far I have this ; <br>
    <br>
    plusplus' :: [a] -> [a] -> [a]<br>
    plusplus' [] (xs) = xs <br>
    plusplus' [] [] = [] <br>
    plusplus' (xs) [] =  xs<br>
    plusplus' (x:xs) yx = plusplus' xs x:yx<br>
    <br>
    main = print . plusplus' $ [1,2] [3,4]<br>
    <br>
    <br>
    But I still get this error message : <br>
    <br>
    <div>src/Main.hs@5:23-5:37 </div>
    <div><span>Couldn't match expected type </span>
      <div style="font-size:14px"><span>a</span></div>
      <span> with actual type </span>
      <div style="font-size:14px">[<span>a</span>]</div>
      <span> </span>
      <div style="font-size:14px"><span>a</span></div>
      <span> is a rigid type variable bound by the type signature for
        plusplus' :: [a] -> [a] -> [a] at
        /home/app/isolation-runner-work/projects/112825/session.207/src/src/Main.hs:1:14
Relevant
        bindings include yx :: [a] (bound at
        /home/app/isolation-runner-work/projects/112825/session.207/src/src/Main.hs:5:18)

        xs :: [a] (bound at
        /home/app/isolation-runner-work/projects/112825/session.207/src/src/Main.hs:5:14)

        x :: a (bound at
        /home/app/isolation-runner-work/projects/112825/session.207/src/src/Main.hs:5:12)

        plusplus' :: [a] -> [a] -> [a] (bound at
/home/app/isolation-runner-work/projects/112825/session.207/src/src/Main.hs:2:1)</span><span title="Click to show/hide extra information"> …<br>
        <br>
        <br>
      </span></div>
    <br>
  
<br><br>
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