Question

The following racket function produces the error:

reference to undefined identifier: val

This is because the eval function looks at the global namespace, not the local function’s namespace. How do I trick eval into using the local function’s namespace?

(define some-eval!
  (lambda (val row col)
    (eval (list 'define 'ttboard '(list-builder val row col))) (current-namespace) ))

Answer 1

You can define ttboard ahead of time and then set! it:

(define ttboard #f)
(define create-board
  (lambda (val row col)
    (set! ttboard (list-builder val row col))))

That way, you can clearly tell that ttboard is a global variable, rather than having its definition obscured in an eval’d clause.