StrMap.fromRecord

create a StrMap from a homogeneous record

Author: matthewleon

bower.json

@@ -26,7 +26,8 @@
     "purescript-lists": "^4.0.0",
     "purescript-st": "^3.0.0",
     "purescript-gen": "^1.1.0",
-    "purescript-foldable-traversable": "^3.6.1"
+    "purescript-foldable-traversable": "^3.6.1",
+    "purescript-typelevel-prelude": "^2.6.0"
   },
   "devDependencies": {
     "purescript-quickcheck": "^4.0.0",

src/Data/StrMap.purs

@@ -16,6 +16,7 @@ module Data.StrMap
   , toAscUnfoldable
   , fromFoldable
   , fromFoldableWith
+  , fromRecord
   , delete
   , pop
   , member
@@ -46,7 +47,6 @@ import Prelude
 
 import Control.Monad.Eff (Eff, runPure, foreachE)
 import Control.Monad.ST as ST
-
 import Data.Array as A
 import Data.Eq (class Eq1)
 import Data.Foldable (class Foldable, foldl, foldr, for_)
@@ -60,6 +60,8 @@ import Data.Traversable (class Traversable, traverse)
 import Data.TraversableWithIndex (class TraversableWithIndex, traverseWithIndex)
 import Data.Tuple (Tuple(..), fst, uncurry)
 import Data.Unfoldable (class Unfoldable)
+import Type.Row.Homogeneous (class Homogeneous)
+import Unsafe.Coerce (unsafeCoerce)
 
 -- | `StrMap a` represents a map from `String`s to values of type `a`.
 foreign import data StrMap :: Type -> Type
@@ -235,6 +237,10 @@ fromFoldableWith f l = pureST (do
   for_ l (\(Tuple k v) -> runFn4 _lookupST v (f v) k s >>= SM.poke s k)
   pure s)
 
+-- | Create a map from a homogeneous record (all attributes have the same type).
+fromRecord :: forall r t. Homogeneous r t => Record r -> StrMap t
+fromRecord = unsafeCoerce
+
 foreign import toArrayWithKey :: forall a b . (String -> a -> b) -> StrMap a -> Array b
 
 -- | Unfolds a map into a list of key/value pairs

test/Test/Data/StrMap.purs

@@ -160,6 +160,10 @@ strMapTests = do
     quickCheck (M.lookup "1" nums == Just 2  <?> "invalid lookup - 1")
     quickCheck (M.lookup "2" nums == Nothing <?> "invalid lookup - 2")
 
+  log "fromRecord"
+  quickCheck (M.fromRecord {a: 1, b: 2, c: 3}
+              == M.fromFoldable [Tuple "a" 1, Tuple "b" 2, Tuple "c" 3])
+
   log "toUnfoldable . fromFoldable = id"
   quickCheck $ \arr -> let f x = M.toUnfoldable (M.fromFoldable x)
                        in f (f arr) == f (arr :: L.List (Tuple String Int)) <?> show arr