Design a polymorphic API

Question

I have a concept of scale that converts an input domain and an output range. However, there are several types of scales; each of them supports a subset of the possible operations and preserves a slightly different range.

For instance:

A ContinuousScale ( Scale (Float, Float) (Float, Float)), which has a domain (Float, Float), and the range (Float, Float)supports:

• convert : Continuous -> Float -> Float convert a value from a domain to a range.
• invert : Continuous -> Float -> Float converts a value from a range back to a domain.
• domain : Continuous -> (Float, Float) return domain.
• ticks : Continuous -> List Float returns values ​​suitable for drawing on an axis.

A mask Sequentialhas a scope (Float, Float)and function out Float -> a; it usually does not make much sense to store a range.

• convert : Sequential a -> Float -> a converts a value from a domain to a range.
• domain : Sequential a -> (Float, Float) return domain.

Scale

A Quantile (List Float) (List a). ; .

• convert : Quantile a -> Float -> a .
• invertExtent : Quantile a -> a -> (Float, Float) , .

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API Elm?

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Answer 1

Scale a ?

type Scale a
  = Continuous (Float, Float) (Float, Float)
  | Sequential (Float, Float) (Float -> a)
  | Quantile (List Float) (Float -> a)

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, case.

convert : Scale a -> Float -> a
convert scale val =
  case scale of
    Continuous domain range -> ...
    Sequential domain mapper -> ...
    Quantile domain mapper -> ...

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invertExtent : Scale a -> a -> Maybe (Float, Float)
invertExtent scale val =
  case scale of
    Continuous _ _ -> Nothing
    Sequential _ _ -> Nothing
    Quantile domain mapper -> Just (...)

Answer 2

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: , : https://gist.github.com/hkgumbs/069437f3e6b75ea15201b36188f6cc7a