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R7RS compatibility issue with Data Labels:

  • R7RS defines a read which violates a core assumption provided by R5RS readers: before s-expressions where known to be directed acyclic graphs, with data labels they are no longer.

    This results in the conflict:

    1. We could either define that we can no longer rely on the SXPath-equivalence of s-expressions an XML including support for constructing XML using Scheme or,
    2. alternatively we limit our reader to be single-pass, compatible with immutable memory access policies etc. and forbid to support data labels in our variant.

Currently the latter is seen as the sane solution.

The same limitation is seen in other Scheme dialects. Those might be worth to watch in case they find a solution:


do we need this link?
4447 created > 2017-11-20 13:34:19 +0100
4448 creator (registered) > jfw

R7RS issues comment