Abstract variable declarations are written using VAR(...):
(VAR("foo", IntClass): Tree)
or in general:
VAR(sym|"x", typ|"C").tree
Value definitions are written as:
VAR("foo", IntClass) := LIT(0)
as a special form of initializing the variable with the default value of the type, WILDCARD can be used as follows:
VAR("foo", IntClass) := WILDCARD
This prints as:
var foo: Int = _