Hacker News Reader

Yeah, that was a pretty dramatic move. It means MzScheme is no longer an implementation of the Scheme standard.

The latest standard, R6RS, goes no further than grumbling about mutable pairs and raising the possibility of deprecating them in the future:

http://www.r6rs.org/final/html/r6rs-rationale/r6rs-rationale...

View on HN

To be fair, the base language of PLT never claimed to support any relevant standard. Instead implementations of standards are built as libraries on top of the base language. So PLT does provide both R5RS and R6RS, both with mutable pairs.

It is when you want to use PLT-specific non-RnRS libraries from RnRS code, you run into pair incompatibilities.

But before this change, I believe every PLT Scheme implementation was a superset of standard Scheme. (Which every Scheme implementation is.) Now it's actually incompatible.

Reply on news.ycombinator.com