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Define Rel8.Table.Maybe.projectMaybe and export it #364

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Define Rel8.Table.Maybe.projectMaybe and export it #364

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2 changes: 1 addition & 1 deletion src/Rel8.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ module Rel8

-- ** @MaybeTable@
, MaybeTable
, maybeTable, ($?), nothingTable, justTable
, maybeTable, ($?), projectMaybe, nothingTable, justTable
, isNothingTable, isJustTable
, fromMaybeTable
, optional
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12 changes: 12 additions & 0 deletions src/Rel8/Table/Maybe.hs
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Expand Up @@ -18,6 +18,7 @@ module Rel8.Table.Maybe
, isNothingTable, isJustTable
, fromMaybeTable
, ($?)
, projectMaybe
, nameMaybeTable
, makeMaybeTable
, unsafeFromJustTable
Expand Down Expand Up @@ -232,6 +233,17 @@ f $? ma@(MaybeTable _ a) = case nullable @b of
infixl 4 $?


-- | If a @'MaybeTable' 'Expr'@ contains a single column, it can be
-- projected into a @'Expr' Maybe@. This is a simple application of
-- @('$?')@, provided for readability.
--
-- @
-- projectMaybe = (id '$?')
-- @
projectMaybe :: DBType a => MaybeTable Expr (Expr a) -> Expr (Maybe a)
projectMaybe = (id $?)


-- | Construct a 'MaybeTable' in the 'Name' context. This can be useful if you
-- have a 'MaybeTable' that you are storing in a table and need to construct a
-- 'TableSchema'.
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