The suggested IR represents tree-ish structure(TreeNode) with a Lisp-like list.
There can be two types of intermediate nodes, namely functions and operators, there are two types of leaf nodes, namely columns and constants. Here is the example of a simple expression, e.g. let c1 be an timestamp column:
floor(c1 + 1.05) < 0

(func "<"

  (func "floor"

   (func "+" (col col1) (const 1.05))) 0)    

The translator should support the revert operation, namely IR to TreeNode conversion.