ExtFunctions = {('http://exslt.org/math', 'abs'): <function Abs>, ('http://exslt.org/math', 'acos'): <function ACos>, ('http://exslt.org/math', 'asin'): <function ASin>, ('http://exslt.org/math', 'atan'): <function ATan>, ('http://exslt.org/math', 'atan2'): <function ATan2>, ('http://exslt.org/math', 'constant'): <function Constant>, ('http://exslt.org/math', 'cos'): <function Cos>, ('http://exslt.org/math', 'exp'): <function Exp>, ('http://exslt.org/math', 'highest'): <function Highest>, ('http://exslt.org/math', 'log'): <function Log>, ...}