Add S.append

index.js

@@ -2274,6 +2274,7 @@
         return n < 0 || negativeZero(n) ? Nothing() : slice(0, -n, xs);
       });
 
+
   //  ArrayLike :: TypeClass
   var ArrayLike = $.TypeClass(
     'ArrayLike',
@@ -2292,6 +2293,24 @@
                R.pipe(R[name], Just, R.filter(R.gte(_, 0))));
   };
 
+  //# append :: a -> Array a -> Array a
+  //.
+  //. Takes a value of any type and an array of values of that type, and
+  //. returns the result of appending the value to the array.
+  //.
+  //. ```javascript
+  //. > S.append(3, [1, 2])
+  //. [1, 2, 3]
+  //.
+  //. > S.append([3, 4], [[1], [2]])
+  //. [[1], [2], [3, 4]]
+  //. ```
+  S.append =
+  def('append',
+      {},
+      [a, $.Array(a), $.Array(a)],
+      function(x, xs) { return xs.concat([x]); });
+
   //# indexOf :: a -> [a] -> Maybe Integer
   //.
   //. Takes a value of any type and a list, and returns Just the index

test/append.js

@@ -0,0 +1,21 @@
+'use strict';
+
+var eq = require('./utils').eq;
+var S = require('..');
+
+describe('append', function() {
+
+  it('adds the element to the end of the list', function() {
+    eq(S.append('c', ['a', 'b']), ['a', 'b', 'c']);
+    eq(S.append({x: 3}, [{x: 1}, {x: 2}]), [{x: 1}, {x: 2}, {x: 3}]);
+  });
+
+  it('adds a list to a list of lists', function() {
+    eq(S.append([3, 4], [[1], [2]]), [[1], [2], [3, 4]]);
+  });
+
+  it('works on empty list', function() {
+    eq(S.append(1, []), [1]);
+  });
+
+});