[Haskell-cafe] [Haskell] ANNOUNCE: Diagrams 1.0

[Henning Thielemann]

Am 18.01.2014 13:25, schrieb Henning Thielemann:

> When compiling I get:
>
> src/Diagrams/TwoD/Layout/Tree.hs:448:26:
>      No instance for (Default (ForceLayoutOpts R2))
>        arising from a use of `def'
>      Possible fix:
>        add an instance declaration for (Default (ForceLayoutOpts R2))
>      In the `_forceLayoutOpts' field of a record
>      In the expression:
>        FLTOpts
>          {_forceLayoutOpts = def, _edgeLen = sqrt 2, _springK = 0.05,
>           _staticK = 0.1}
>      In an equation for `def':
>          def
>            = FLTOpts
>                {_forceLayoutOpts = def, _edgeLen = sqrt 2, _springK = 0.05,
>                 _staticK = 0.1}

I guess this problem is best fixed by staying away from data-default, at 
all. I can't believe it is sensible to assign default values to 
arbitrary types.