Add singleton

.gitignore

@@ -1,4 +1,6 @@
-bower_components
-output
-.psci
-.psci_modules
+/.*
+!/.gitignore
+!/.travis.yml
+/bower_components/
+/node_modules/
+/output/

.travis.yml

@@ -0,0 +1,14 @@
+language: node_js
+sudo: false
+node_js:
+  - 0.10
+env:
+  - PATH=$HOME/purescript:$PATH
+install:
+  - TAG=$(wget -q -O - https://github.com/purescript/purescript/releases/latest --server-response --max-redirect 0 2>&1 | sed -n -e 's/.*Location:.*tag\///p')
+  - wget -O $HOME/purescript.tar.gz https://github.com/purescript/purescript/releases/download/$TAG/linux64.tar.gz
+  - tar -xvf $HOME/purescript.tar.gz -C $HOME/
+  - chmod a+x $HOME/purescript
+  - npm install
+script:
+  - npm run build

docs/Data/NonEmpty.md

@@ -29,6 +29,14 @@ instance foldableNonEmpty :: (Foldable f) => Foldable (NonEmpty f)
 instance traversableNonEmpty :: (Traversable f) => Traversable (NonEmpty f)
 ```
 
+#### `singleton`
+
+``` purescript
+singleton :: forall f a. (Plus f) => a -> NonEmpty f a
+```
+
+Create a non-empty structure with a single value.
+
 #### `(:|)`
 
 ``` purescript

package.json

@@ -0,0 +1,11 @@
+{
+  "private": true,
+  "scripts": {
+    "postinstall": "pulp dep install",
+    "build": "pulp test && rimraf docs && pulp docs"
+  },
+  "devDependencies": {
+    "pulp": "^4.0.1",
+    "rimraf": "^2.4.1"
+  }
+}

src/Data/NonEmpty.purs

@@ -3,6 +3,7 @@
 
 module Data.NonEmpty
   ( NonEmpty(..)
+  , singleton
   , (:|)
   , foldl1
   , foldMap1
@@ -13,8 +14,9 @@ module Data.NonEmpty
 
 import Prelude
 
-import Control.Alternative (Alternative)
 import Control.Alt ((<|>))
+import Control.Alternative (Alternative)
+import Control.Plus (Plus, empty)
 
 import Data.Foldable (Foldable, foldl, foldr, foldMap)
 import Data.Traversable (Traversable, traverse, sequence)
@@ -31,6 +33,10 @@ data NonEmpty f a = NonEmpty a (f a)
 
 infix 5 :|
 
+-- | Create a non-empty structure with a single value.
+singleton :: forall f a. (Plus f) => a -> NonEmpty f a
+singleton a = NonEmpty a empty
+
 -- | An infix synonym for `NonEmpty`.
 (:|) :: forall f a. a -> f a -> NonEmpty f a
 (:|) = NonEmpty