Merge pull request #39 from purescript/revert-38-revert-37-bounded-char-instance

Revert "Revert "Add Bounded Char instance""

Author: paf31

docs/Prelude.md

@@ -836,6 +836,12 @@ _left-associative / precedence 4_
 
 Test whether one value is _non-strictly greater than_ another.
 
+#### `unsafeCompare`
+
+``` purescript
+unsafeCompare :: forall a. a -> a -> Ordering
+```
+
 #### `Bounded`
 
 ``` purescript
@@ -860,6 +866,7 @@ instance boundedBoolean :: Bounded Boolean
 instance boundedUnit :: Bounded Unit
 instance boundedOrdering :: Bounded Ordering
 instance boundedInt :: Bounded Int
+instance boundedChar :: Bounded Char
 instance boundedFn :: (Bounded b) => Bounded (a -> b)
 ```
 
@@ -881,6 +888,7 @@ instance boundedOrdBoolean :: BoundedOrd Boolean
 instance boundedOrdUnit :: BoundedOrd Unit
 instance boundedOrdOrdering :: BoundedOrd Ordering
 instance boundedOrdInt :: BoundedOrd Int
+instance boundedOrdChar :: BoundedOrd Char
 ```
 
 #### `BooleanAlgebra`
@@ -975,9 +983,4 @@ instance showArray :: (Show a) => Show (Array a)
 instance showOrdering :: Show Ordering
 ```
 
-#### `unsafeCompare`
 
-``` purescript
-unsafeCompare :: forall a. a -> a -> Ordering
-```
-The `unsafeCompare` function is mainly intended for module writers supporting native types via the FFI, and not for general comparisons.

src/Prelude.js

@@ -172,7 +172,12 @@ exports.unsafeCompareImpl = function (lt) {
   };
 };
 
-//- Lattice --------------------------------------------------------------------
+//- Bounded --------------------------------------------------------------------
+
+exports.topChar = String.fromCharCode(65535);
+exports.bottomChar = String.fromCharCode(0);
+
+//- BooleanAlgebra -------------------------------------------------------------
 
 exports.boolOr = function (b1) {
   return function (b2) {
@@ -186,8 +191,6 @@ exports.boolAnd = function (b1) {
   };
 };
 
-//- ComplementedLattice --------------------------------------------------------
-
 exports.boolNot = function (b) {
   return !b;
 };

src/Prelude.purs

@@ -737,10 +737,18 @@ instance boundedInt :: Bounded Int where
   top = 2147483647
   bottom = -2147483648
 
+-- | Characters fall within the Unicode range.
+instance boundedChar :: Bounded Char where
+  top = topChar
+  bottom = bottomChar
+
 instance boundedFn :: (Bounded b) => Bounded (a -> b) where
   top _ = top
   bottom _ = bottom
 
+foreign import topChar :: Char
+foreign import bottomChar :: Char
+
 -- | The `BoundedOrd` type class represents totally ordered finite data types.
 -- |
 -- | Instances should satisfy the following law in addition to the `Ord` laws:
@@ -752,6 +760,7 @@ instance boundedOrdBoolean :: BoundedOrd Boolean where
 instance boundedOrdUnit :: BoundedOrd Unit where
 instance boundedOrdOrdering :: BoundedOrd Ordering where
 instance boundedOrdInt :: BoundedOrd Int where
+instance boundedOrdChar :: BoundedOrd Char where
 
 -- | The `BooleanAlgebra` type class represents types that behave like boolean
 -- | values.