Add elem and elem1 to Rel8.Array

Author: shane-circuithub

changelog.d/20250701_105439_shane.obrien_elem.md

@@ -0,0 +1,3 @@
+### Added
+
+- Add `elem` and `elem1` to `Rel8.Array` for testing if an element is contained in `[]` and `NonEmpty` `Expr`s.

src/Rel8/Array.hs

@@ -1,3 +1,7 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE MonoLocalBinds #-}
+{-# LANGUAGE OverloadedStrings #-}
+
 module Rel8.Array
   (
     -- ** @ListTable@
@@ -6,13 +10,15 @@ module Rel8.Array
   , index, indexExpr
   , last, lastExpr
   , length, lengthExpr
+  , elem
 
     -- ** @NonEmptyTable@
   , NonEmptyTable
   , head1, head1Expr
   , index1, index1Expr
   , last1, last1Expr
   , length1, length1Expr
+  , elem1
 
     -- ** Unsafe
   , unsafeSubscript
@@ -21,11 +27,34 @@ module Rel8.Array
 where
 
 -- base
-import Prelude hiding (head, last, length)
+import Data.List.NonEmpty (NonEmpty)
+import Prelude hiding (elem, head, last, length)
 
 -- rel8
+import Rel8.Expr (Expr)
+import Rel8.Expr.Array (listOf, nonEmptyOf)
+import Rel8.Expr.Function (rawBinaryOperator)
 import Rel8.Expr.List
 import Rel8.Expr.NonEmpty
 import Rel8.Expr.Subscript
+import Rel8.Schema.Null (Sql)
 import Rel8.Table.List
 import Rel8.Table.NonEmpty
+import Rel8.Type.Eq (DBEq)
+
+
+-- | @'elem' a as@ tests whether @a@ is an element of the list @as@.
+elem :: Sql DBEq a => Expr a -> Expr [a] -> Expr Bool
+elem = (<@) . listOf . pure
+  where
+    (<@) = rawBinaryOperator "<@"
+infix 4 `elem`
+
+
+-- | @'elem1' a as@ tests whether @a@ is an element of the non-empty list
+-- @as@.
+elem1 :: Sql DBEq a => Expr a -> Expr (NonEmpty a) -> Expr Bool
+elem1 = (<@) . nonEmptyOf . pure
+  where
+    (<@) = rawBinaryOperator "<@"
+infix 4 `elem1`