Added currying snippet.

core/functions.ipynb

@@ -361,6 +361,75 @@
       }
      ],
      "prompt_number": 7
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## Currying"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Currying means to derive new functions from existing ones by partial argument appilcation.  Currying is used in pandas to create specialized functions for transforming time series data.\n",
+      "\n",
+      "The argument y in add_numbers is curried:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "def add_numbers(x, y):\n",
+      "    return x + y\n",
+      "\n",
+      "add_seven = lambda y: add_numbers(7, y)\n",
+      "add_seven(3)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 18,
+       "text": [
+        "10"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "The built-in functools can simplify currying with partial:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "from functools import partial\n",
+      "add_five = partial(add_numbers, 5)\n",
+      "add_five(2)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 19,
+       "text": [
+        "7"
+       ]
+      }
+     ],
+     "prompt_number": 19
     }
    ],
    "metadata": {}