On 8/8/11 1:59 PM, Simon Michael wrote:
And, I may have made things worse for myself in the reuse/avoiding
boilerplate department: I'm not sure how to reuse a cmdargs options data
structure, extending it with a few more options.
This is a big problem I'm dealing with too lately. In particular, what I
would like is if cmdargs could do flattening of structures, either
automatically or with a new annotation combinator. With this it would be
easy to have a basic FooBar program:
data FooBar = FooBar
{ foo :: Foo
, bar :: Bar
}
deriving (Data, Typeable,...)
getFooBarMode :: IO (Mode (CmdArgs FooBar))
getFooBarMode = ...
and then extend it to a FooBarBaz program:
data FooBarBaz = FooBarBaz
{ fooBar :: FooBar
, baz :: Baz
}
deriving (Data, Typeable,...)
getFooBarBazMode :: IO (Mode (CmdArgs FooBarBaz))
getFooBarBazMode = ...
The big trick is that I should be able to call getFooBarMode from
getFooBarBazMode equivalently to if I had defined,
data FooBarBaz = FooBarBaz
{ foo :: Foo
, bar :: Bar
, baz :: Baz
}
deriving (Data, Typeable,...)
and copied over getFooBarMode inline into getFooBarBazMode. The problem
is that the bulk of the code is in the Mode-generating functions, and
it's also the sort of code that's hardest to keep in sync
documentation-wise.
I don't mind the extra indirection in the Mode structures since I don't
actually use them in the program itself; I have an internal
configuration type that I compile the FooBarBaz down to, so that I can
perform additional semantic consistency checks before execution, as well
as precomputing what the commandline arguments dereference into (e.g.,
functions).
As always, thanks a lot for cmdargs!
-Simon
Indeed. Aside from this feature request I've been quite pleased :)
--
Live well,
~wren
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