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| author | Joey Hess <joeyh@joeyh.name> | 2017-07-13 23:42:17 -0400 |
|---|---|---|
| committer | Joey Hess <joeyh@joeyh.name> | 2017-07-13 23:42:17 -0400 |
| commit | 020dafc4203a37a57d3a6da12708dc170921c9c6 (patch) | |
| tree | d4b7e545341e84e0c33c4a61b5e4da1758db2889 /doc/todo/differential_update_via_RevertableProperty.mdwn | |
| parent | b72be10661f96976dd3741943313dd7fccf3d782 (diff) | |
rollbacks
Diffstat (limited to 'doc/todo/differential_update_via_RevertableProperty.mdwn')
| -rw-r--r-- | doc/todo/differential_update_via_RevertableProperty.mdwn | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/doc/todo/differential_update_via_RevertableProperty.mdwn b/doc/todo/differential_update_via_RevertableProperty.mdwn index 6c217944..6d65c916 100644 --- a/doc/todo/differential_update_via_RevertableProperty.mdwn +++ b/doc/todo/differential_update_via_RevertableProperty.mdwn @@ -99,7 +99,7 @@ fooisfoo = foo ==# foo Is, perhaps: data Version = A | B | C - deriving (Ord) + deriving (Enum, Ord) foo :: Versioned Host foo = versionedHost "foo" $ do @@ -112,9 +112,11 @@ That's ... pretty ok, would hit as least some of the use cases described above. Seems to need a Reader+Writer monad to implement it, without passing the Version around explicitly. -Note that it's allowable for `somethingelse` to not be revertable, -since once `foo` gets that property, it is never removed. -So, `inVersion` has to accept both `RevertableProperty` and `Property`. +Is it allowable for `somethingelse` to not be revertable? +Once `foo` gets that property, it is never removed if we're moving only +forwars. On the other hand, perhaps the user will want to roll back to +version A. Allowing rollbacks seems good, so `inVersion` should only +accept `RevertableProperty`. Here's another situation where reversion is not needed: |