Using Either recursively

Asked Nov 03 '20 at 22:16

Active Nov 03 '20 at 22:44

Viewed 133 times

So I have defined a function like this one below:

myFunction :: String -> Either String MyType

I am reading String until the end. Left is used for handling errors. Right suppose to return me the tuple. In myFunction I am calling anotherFunction and checking if it returns Left or Right like this:

myFunction :: String -> Either String MyType
myFunction "" = Right -- want to return MyType here
myFunction s = 
     case anotherFunction s of
         Left c -> Left c
         Right (v1, v2, t) -> -- want to call myFunction again with t

When anotherFunction returns Right, I want to call myFunction again recursively without loosing v1 and v2. How can I achieve that with recursion?

Here is the exact definition of MyType:

data MyType = MyString String | MyInt Int | MyMap [(String, MyType)] deriving (Show, Eq)

edited Nov 03 '20 at 22:44

asked Nov 03 '20 at 22:16

dekanidze

It's a bit unclear what you're asking, but I think what you want is just the `>>=` operator. http://idownvotedbecau.se/noattempt/ – leftaroundabout Nov 03 '20 at 22:22
1

I think it would help if you add a simple example. For example some mapping from a `Char` to some 2-tuple of `Int`s to illustrate what you aim to do. – Willem Van Onsem Nov 03 '20 at 22:24
What is `MyType`? – David Young Nov 03 '20 at 22:36
MyType has a JLMap [(String, MyType)] which is, I believe, needed here – dekanidze Nov 03 '20 at 22:39
@Aivaras Could you give the exact definition of `MyType`? – David Young Nov 03 '20 at 22:42
@David yes, edited my question – dekanidze Nov 03 '20 at 22:45
What I want to achieve here is to add v1 and v2 to a tuple and add that tuple to a list, where list could have more than one tuple. And at the end return my desired list – dekanidze Nov 03 '20 at 22:59
Looks like `MyType` is some sort of generic "value" type. It will need to be able to represent lists of tuples, which it currently does not, if you want to add a tuple to a list and call it a `MyType`. – luqui Nov 04 '20 at 04:43

Using Either recursively

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