haskell problems with Data.Map update <p>I am trying to edit the vertices. I can add to it, but when I use update I get:</p> <pre><code>Couldn't match expected type `(GLfloat, GLfloat, GLfloat) -&gt; Maybe (GLfloat, GLfloat, GLfloat)' with actual type `(t0, t1, t2)' In the first argument of `Map.update', namely `(- 0.75, 0.25, 0.0)' In the expression: Map.update (- 0.75, 0.25, 0.0) "v1" faceMap In an equation for `it': it = Map.update (- 0.75, 0.25, 0.0) "v1" faceMap </code></pre> <hr> <pre><code>import qualified Data.Map as Map import Graphics.UI.GLUT import Graphics.Rendering.OpenGL faceMap :: Map.Map [Char] (GLfloat, GLfloat, GLfloat) faceMap = Map.fromList $ [("v1", (-0.25, 0.25, 0.0 )) ,("v1", (0.75, 0.35, 0.0)) ,("v3", (0.75, -0.15, 0.0)) ,("v4", (-0.75, -0.25, 0.0)) ] </code></pre> <hr> <p>If you know another way other than editing values that would be great, and yes this is OpenGL.</p>