Hi,

I am thinking now to allow extending 'expr' syntax using identifier
properties. The current implementation of 'expr' syntax [1] allows
extension through table defining the operation. But using identifier
properties look promising and much more flexible.

However, while looking at SRFI-213, it seems that 'define-property'
isn't widely implemented: Unsyntax and Chez Scheme. So I wonder if it
is wasting time to work on that? Though?

Regards

[1] latest version in https://github.com/jobol/srfi-266 can be used
 in guile and Chez Scheme