The third argument to identifier-binding, top-level-symbol?, controls the 
result of identifier-binding when the identifier is bound to a top-level 
binding (and both the REPL and sandboxed evaluators are kinds of top-level 
evaluation). The docs elaborate this way:
> The result is (list source-id) if id-stx has a top-level binding and 
> top-level-symbol? is true.
> The result is #f if id-stx has a top-level binding and top-level-symbol? is 
> #f or if id-stx is unbound. An unbound identifier is typically treated the 
> same as an identifier whose top-level binding is a variable.

I’m not actually sure what the full implications are of passing #t for that 
argument, but you might try that and see if it works for you. A disadvantage of 
using syntax-local-value is that it will fail if the identifier is bound to a 
runtime variable rather than syntax.


> On Apr 20, 2019, at 16:56, Ryan Kramer <> wrote:
> Below is a short example showing that identifier-binding doesn't seem to work 
> quite right with Scribble's make-base-eval. It works fine with make-evaluator 
> from racket/sandbox.
> I'm not sure why this is, but using syntax-local-value instead works 
> everywhere. (Implementation here: 
> #lang racket
> (require scribble/eval
>          racket/sandbox)
> (define (setup eval)
>   (eval
>    '(define-syntax (define-if-not stx)
>       (syntax-case stx ()
>         [(_ id val)
>          (identifier-binding #'id)
>          #'(void)]
>         [(_ id val)
>          #'(define id val)]))))
> (define scribble-eval (make-base-eval))
> (scribble-eval '(require racket))
> (setup scribble-eval)
> (define racket-eval (make-evaluator 'racket))
> (setup racket-eval)
> (scribble-eval '(define-if-not foo 1))
> (scribble-eval '(define-if-not foo 2))
> (scribble-eval 'foo) ; want 1, get 2
> (racket-eval '(define-if-not bar 3))
> (racket-eval '(define-if-not bar 4))
> (racket-eval 'bar) ; want 3, get 3

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