Re: [Haskell-beginners] Reducing local variable duplication

29 Aug 2011


      The where block takes precedence over the global scope so if these points
are generally reused for most tests and only deviate in a few, you could
define them globally to the file and then modify individual ones in the
where blocks of code that needs different values.

Hope that helps

On Mon, Aug 29, 2011 at 8:35 AM, Michael Orlitzky wrote:
...
I have a series of unit tests like this,
...
test_volume1 :: Assertion
test_volume1 =
  assertEqual "volume is correct" True (vol ~= (-1/3))
  where
    p0 = (0, -0.5, 0)
    p1 = (0, 0.5, 0)
    p2 = (2, 0, 0)
    p3 = (1, 0, 1)
    ...
test_volume2 :: Assertion
test_volume2 =
  assertEqual "volume is correct" True (vol ~= (1/3))
  where
    p0 = (0, -0.5, 0)
    p1 = (2, 0, 0)
    p2 = (0, 0.5, 0)
    p3 = (1, 0, 1)
    ...
I would like to de-duplicate some of the values in the 'where' clause.
Furthermore, I don't want to declare e.g. p0 and p3 at the top level,
since later tests may need different values of p0,p3. What I would
really like is something like the following. Is it possible?
...
let p0 = (0, -0.5, 0)
    p3 = (1, 0, 1)
in
  test_volume1 :: Assertion
  test_volume1 =
    assertEqual "volume is correct" True (vol ~= (-1/3))
    where
      p1 = (0, 0.5, 0)
      p2 = (2, 0, 0)
      ...
test_volume2 :: Assertion
  test_volume2 =
    assertEqual "volume is correct" True (vol ~= (1/3))
    where
      p1 = (2, 0, 0)
      p2 = (0, 0.5, 0)
      ...
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