Transforming parse to PAST

...into a semantic tree equivalent

Stmts:
  Op: bind
    Var: a
    Val: 1
  Op: while
    Expression: infix:<=
      Var: a
      Val: 10
    Stmts:
      Op: print
        Var: a
      Op: bind
        Var: a
        Op: infix:+
          Var: a
          Val: 1