wiki:UndecidableInstances

Version 3 (modified by ross@…, 9 years ago) (diff)

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Allow Undecidable Instances

Ticket(s)

See ExtensionDescriptionHowto for information on how to write these extension descriptions. Please add any new extensions to the list of HaskellExtensions.

Brief Explanation

There are no restrictions on the form of instance declarations (see FlexibleInstances). As a result, context reduction need not terminate, so implementations impose some limit on the depth of inference.

References

Pros

  • offered by GHC and Hugs with appropriate options
  • flexible

Cons

  • no clear boundary