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Re: regexp and valid-sre?

On 11/26/2013 1:46 PM, Arthur A. Gleckler wrote:
On Tue, Nov 26, 2013 at 1:29 PM, Michael Montague <mikemon@xxxxxxxxx> wrote:
I just briefly looked through the documentation for GNU Emacs and could not find the equivalent of  'valid-sre?'.
Much of that code is written in C.  It would clearly be useful to be able to give a user an error message about having typed an invalid regular _expression_ when using `re-search-forward', for example.
Why does it matter if the code is written in C or Scheme? The code that calls re-search-forward can use guard to catch the exception raised by an invalid regular _expression_. Why were exceptions put into R7RS if we are not going to use them? Is the issue that 'valid-sre?' predates portable support for exception handling in Scheme?