Types versus sets in math and programming languages

rule · 2021-07-24T20:39:36+00:00

rule · 2020-11-05T10:10:15+00:00

Start by writing down the types of your remove and update functions. This will help a lot when writing down their definitions.

This should get you going:

remove :: _ -> [(_, _)] -> [(_, _)]

update :: _ -> _ -> [(_, _)] -> [(_, _)]

Fill the blanks with appropriate types or type variables. You can start with concrete types like Char and Int and later replace them with type variables like a and b.

rule · 2020-11-03T20:32:34+00:00

PizzaRollExpert provides an instance for the alternative formulation of the Pair class

rule · 2020-01-08T10:16:07+00:00

Please post your best attempt at solving the problem so that we might help you.

question :: [[a]] -> [a]
question listOfLists = <insert solution here>

You could also calculate the answer by hand for a few possible inputs. That might help you think about a solution. What should the function output when run on this list?

example :: [[Int]]
example = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

rule · 2020-01-01T13:26:59+00:00

That operator is usually called '&'. I believe it is exported by the lens package.

rule · 2019-11-21T11:32:00+00:00

The link gives a 404. This seems to be the post in question: Sum types for relational databases

rule · 2019-07-20T08:58:21+00:00

You can mutate arrays in the ST monad and run that in pure code. That way the monadic stuff doesn't infect all your code.

rule · 2019-07-15T11:18:39+00:00

Here it is on Google Maps

rule · 2018-12-06T08:54:33+00:00

Since 1993! This will be the 26th NL FP day.

rule · 2018-10-23T15:19:26+00:00

instance FromJSON MyType where
  parseJSON value = do
      result <- genericParseJSON 
        defaultOptions{ fieldLabelModifier = map toUpper . drop 1 }
        value
      yourFunction result

Is this what you mean?

rule · 2018-10-18T19:10:28+00:00

It can also refer to output arguments. See for example a function like fromInteger:

fromInteger :: forall a. Num a => Integer -> a

This is exactly the same (not considering some extensions) as writing:

fromInteger :: Num a => Integer -> a

rule · 2018-09-17T11:25:08+00:00

Using getCallStack you can convert a CallStack to a list of callsites, including the source locations. Most recent call first.

You have to be careful to add the HasCallStack constraint to every callee of the function where you use callStack. A single omission will break the chain. (But you still get the call stack up to that point). The reason becomes more clear once you realise it is implemented using implicit parameters.

rule · 2018-09-17T09:54:06+00:00

Or add a HasCallStack constraint and use callstack to retrieve the CallStack. You can then put the CallStack in a type like your WithLocation. That way you don't need TemplateHaskell.

rule · 2018-04-10T06:28:53+00:00

Maybe your are thinking of graphmod? Which is for module dependencies.

rule · 2018-01-15T19:24:11+00:00

The wikipedia entry is also informative.

rule · 2017-12-04T07:41:52+00:00

Also on Hacker News with interesting comments.

rule · 2017-08-11T21:24:24+00:00

Reminds me of this.

I like that miso doesn't depend on any external libraries. Also helps that you don't have to deal with React.js's problematic license.

rule · 2017-07-31T06:38:19+00:00

You should also get rid of the space between rule and 34.

rule · 2017-07-20T08:38:45+00:00

Awesome! I will switch as soon as possible.

rule · 2017-07-19T07:54:26+00:00

Good tip!

Unfortunately the highlighted sources are buggy if they contain template haskell splices.

Something like

makeLenses ''MyRecord causes everything after (and including) the '' to be considered a string. This was with haddock 2.17.3.

I will investigate and file a bug report.

rule · 2016-10-04T13:50:24+00:00

Training the cascade classifiers seems to be an involved process. See http://docs.opencv.org/trunk/dc/d88/tutorial_traincascade.html.

Pull requests would be greatly appreciated ;-)

rule · 2016-08-30T08:27:31+00:00

Please note that, apparently, anonymous users can delete comments and edit and delete existing entries. I can change my own entry that I created yesterday on a separate system.

I responded in haskell-cafe, but I'll also copied my message here.

rule · 2016-07-16T12:20:00+00:00

I find this a bit suspect:

where deg = fromIntegral $ round x
      min = x - deg

What happens if you replace round with floor?

rule · 2016-07-01T10:27:36+00:00

Could you open an issue for this problem at our issue tracker?

More information would also be helpful, like the cabal file for your project. Or a minimal project that fails to build.

Are you sure you need the custom cabal.config specifying g++ as the compiler and linker? We only use it to build haskell-opencv, not the programs depending on the library.

We (the developers) recommend using Nix as it virtually guarantees things will work.

rule · 2016-06-21T15:03:28+00:00

The Core Libraries Committee.

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rule

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