Merge pull request #9832 from bcoca/math_filters

math filters!

docsite/rst/playbooks_variables.rst

@@ -311,6 +311,39 @@ To get a random list from an existing  list::
 
 note that when used with a non 'listable' item it is a noop, otherwise it always returns a list
 
+
+.. _math_stuff:
+
+Math
+--------------------
+.. versionadded:: 1.9
+
+
+To see if something is actually a number::
+
+    {{ myvar | isnan }}
+
+Get the logarithm (default is e)::
+
+    {{ myvar | log }}
+
+Get the base 10 logarithm::
+
+    {{ myvar | log(10) }}
+
+Give me the power of 2! (or 5)::
+
+    {{ myvar | pow(2) }}
+    {{ myvar | pow(5) }}
+
+Square root, or the 5th::
+
+    {{ myvar | root }}
+    {{ myvar | root(5) }}
+
+Note that jinja2 already provides some like abs() and round().
+
+
 .. _other_useful_filters:
 
 Other Useful Filters

lib/ansible/runner/filter_plugins/math.py

@@ -0,0 +1,67 @@
+# (c) 2014, Brian Coca <bcoca@ansible.com>
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+import math
+from ansible import errors
+
+def isnotanumber(x):
+    try:
+        return math.isnan(x)
+    except TypeError, e:
+        return False
+
+
+def logarithm(x, base=math.e):
+    try:
+        if base == 10:
+            return math.log10(x)
+        else:
+            return = math.log(x, base)
+    except TypeError, e:
+        raise errors.AnsibleFilterError('log() can only be used on numbers: %s' % str(e))
+
+
+def power(x):
+    try:
+        return math.pow(x,y)
+    except TypeError, e:
+        raise errors.AnsibleFilterError('pow() can only be used on numbers: %s' % str(e))
+
+
+def inversepower(x, base=2):
+    try:
+        if base == 2:
+            return math.sqrt(x)
+        else:
+            return math.pow(x, 1.0/float(base))
+    except TypeError, e:
+        raise errors.AnsibleFilterError('root() can only be used on numbers: %s' % str(e))
+
+
+class FilterModule(object):
+    ''' Ansible math jinja2 filters '''
+
+    def filters(self):
+        return {
+            # general math
+            'isnan': isnotanumber,
+
+            # exponents and logarithms
+            'log': logarithm,
+            'pow': power,
+            'root': inversepower,
+        }