Major Description
Today, we are implementing named argument support for user defined functions, some built-in functions, and table-valued functions. For the first step towards building such a feature, we need to make some requisite changes in the parser.
To accomplish this, in this issue, we plan to add some new syntax tokens to the parser in Spark. Changes will also be made in the abstract syntax tree builder as well to reflect these new tokens. Such changes will first be restricted to normal function calls (table value functions will be treated separately).
