ExpressionFunctions class

Definition of default built-in functions for expressions.

<remarks> These functions are largely from WDL https://docs.microsoft.com/en-us/azure/logic-apps/workflow-definition-language-functions-reference with a few extensions like infix operators for math, logic and comparisons. This class also has some methods that are useful to use when defining custom functions. You can always construct a <see cref="ExpressionEvaluator"/> directly which gives the maximum amount of control over validation and evaluation. Validators are static checkers that should throw an exception if something is not valid statically. Evaluators are called to evaluate an expression and should try not to throw. There are some evaluators in this file that take in a verifier that is called at runtime to verify arguments are proper. </remarks>