Re: [Haskell-cafe] Haskell Data Structure design

8 Jul 2016

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On Fri, Jul 8, 2016 at 9:57 PM, Guru Devanla  wrote:
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1.  I see that almost in every function I deal with state, I have e <- get , expression in the begining. I always ending up having to use the state to query for different values. I guess this is OK.
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El 8 jul 2016, a las 22:07, William Yager  escribió:
For #1, look into using the Lens library's support for the State monad. You can often avoid doing a get, and instead write things like `fees += 5`, which will add 5 to the field in the state called "fees".
Lens is a pretty heavy extra thing for a beginner to have to learn -- you'll do fine with the 'modify' function:

modify :: (s -> s) -> State s ()

So instead of writing:

do
   s <- get
   put (s + 5)

You say:

modify (+5)

Tom

Re: [Haskell-cafe] Haskell Data Structure design

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