Merge pull request #2 from purescript/crash

Add crash and crashWith

Author: paf31

docs/Partial.md

@@ -0,0 +1,21 @@
+## Module Partial
+
+Some partial helper functions.
+
+#### `crash`
+
+``` purescript
+crash :: forall a. (Partial) => a
+```
+
+A partial function which crashes on any input with a default message.
+
+#### `crashWith`
+
+``` purescript
+crashWith :: forall a. (Partial) => String -> a
+```
+
+A partial function which crashes on any input with the specified message.
+
+

docs/Partial/Unsafe.md

@@ -10,4 +10,12 @@ unsafePartial :: forall a. (Partial => a) -> a
 
 Discharge a partiality constraint, unsafely.
 
+#### `unsafeCrashWith`
+
+``` purescript
+unsafeCrashWith :: forall a. String -> a
+```
+
+A function which crashes with the specified error message.
+
 

src/Partial.js

@@ -0,0 +1,9 @@
+"use strict";
+
+// module Partial
+
+exports.crashWith = function() {
+    return function(msg) {
+        throw new Error(msg);
+    };
+};

src/Partial.purs

@@ -0,0 +1,12 @@
+-- | Some partial helper functions.
+module Partial 
+  ( crash
+  , crashWith
+  ) where
+
+-- | A partial function which crashes on any input with a default message.
+crash :: forall a. Partial => a
+crash = crashWith "Partial.crash: partial function"
+
+-- | A partial function which crashes on any input with the specified message.
+foreign import crashWith :: forall a. Partial => String -> a

src/Partial/Unsafe.purs

@@ -1,7 +1,12 @@
 -- | Utilities for working with partial functions.
 module Partial.Unsafe 
   ( unsafePartial
+  , unsafeCrashWith
   ) where
 
 -- | Discharge a partiality constraint, unsafely.
 foreign import unsafePartial :: forall a. (Partial => a) -> a
+
+-- | A function which crashes with the specified error message.
+unsafeCrashWith :: forall a. String -> a
+unsafeCrashWith msg = unsafePartial (Partial.crashWith msg)

test/Main.purs

@@ -1,12 +1,11 @@
 module Test.Main where
 
-data X = X | Y
+f :: Partial => Int -> Int
+f 0 = 0
+f _ = Partial.crashWith "f: partial function"
 
-f :: Partial => X -> X
-f X = X
-
-safely :: X
-safely = Partial.Unsafe.unsafePartial (f X)
+safely :: Int
+safely = Partial.Unsafe.unsafePartial (f 0)
 
 main :: forall a. a -> {}
 main _ = {}