Thanks for finding this discrepancy. Actually it's the implementation that is wrong. String->symbol is banned because in some implementations symbols are not garbage-collected, so using it in the sandbox can consume resources to the main program that it can't do anything about.

On Mon, Feb 24, 2020 at 2:56 AM CHIBA Masaomi <xxxxxx@gmail.com> wrote:

Hi,
I found a missing symbol in documentation.
The missing symbol is `string->symbol`.
It contained in reference implementation but not in documentation.
https://github.com/scheme-requests-for-implementation/srfi-172/blob/d13a1174cb638155bbb008eb92d5fd3311e79622/srfi-172-functional.sld#L43

my pull request is here:
https://github.com/scheme-requests-for-implementation/srfi-172/pull/4

Regards,
Masaomi CHIBA