Re: [Haskell-cafe] Looking for feedback on my attempt at a tree construction edsl

On Tue, Mar 22, 2011 at 2:20 PM, Edward Kmett wrote:

If you add an instance of IsString to handle leaf construction you can get it down to     "Fruits" +> do        "Apple"        "Mango"     "Arbitrary" +> do        "1"        "..." But I also don't see the point of doing this in a monad.

Having it in a monad has the same benefit as blaze-html being built in a monad: the square braces and comas for the list are gone. Although it does leave you with an awkward type parameter hanging around. And the same as the Binary Put monad vs. the Binary Builder type. I prefer the monoid interface vs. the monad interface to both of these, but I can see the appeal. Antoine

-Edward

On Tue, Mar 22, 2011 at 1:15 PM, Yves Parès wrote:

...

You could turn 'insertSubTree' into and operator, and shorten "insertLeaf"

createTree = do     "Fruits" +> do                 leaf "Apple"                 leaf "Mango     "Arbitrary" +> do                    leaf "1"     -- and so on...

It's a little bit more concise. But I fail to see the use of TreeContext being an instance of Monad.

2011/3/22 C K Kashyap

...

Hi, With my "edsl", one can describe a tree like this - import TreeEdsl import Data.Tree createTree :: TreeContext String () createTree = do insertSubTree "Fruits" $ do insertLeaf "Apple" insertLeaf "Mango" insertSubTree "Arbitrary" $ do insertSubTree "Numbers" $ do insertLeaf "1" insertLeaf "2" insertLeaf "3" insertSubTree "Letters" $ do insertLeaf "A" insertLeaf "B" insertLeaf "C" return () main = do tree <- process "root" createTree putStrLn (drawTree (fmap show tree)) return ()

and get a tree like this - "root" | +- "Arbitrary" |  | |  +- "Letters" |  |  | |  |  +- "C" |  |  | |  |  +- "B" |  |  | |  |  `- "A" |  | |  `- "Numbers" |     | |     +- "3" |     | |     +- "2" |     | |     `- "1" | `- "Fruits"    |    +- "Mango"    |    `- "Apple"

My code is here

https://github.com/ckkashyap/LearningPrograms/blob/master/Haskell/edsl/TreeE... I'd appreciate your feedback on this. Does this qualify to be a edsl? Regards, Kashyap _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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