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Re: hygiene when using multiple instances of a macro..?

This page is part of the web mail archives of SRFI 72 from before July 7th, 2015. The new archives for SRFI 72 contain all messages, not just those from before July 7th, 2015.

 Hello Panu,
 > Rewrite-based identifier systems are often vulnerable to situations
 > where the same definition is used multiple times in the same rewriting
 > context.  For example, if one has a macro that gets another macro as
 > input (is this possible in the system?) and contains some free variable,
 > and you give it as input to itself, is the outer instance of the macro
 > able to capture the free variable of the inner instance of the macro?
 If I understand correctly, the answer no, hygiene will prevent that from 
 happening.  But if you are able to sketch an example (even if not fully
 fleshed out, or in pseudocode), I would be able to give you a more precise