Scheme Request for Implementation 181,
"Custom ports,"
by John Cowan,
is now available for discussion.

Its draft and an archive of the ongoing discussion are available at

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Here's the abstract:

This is an extract from the R6RS that documents its support for custom ports. These provide a hook into the Scheme port system from below, allowing the creation of binary and textual ports that behave exactly like file, string, and bytevector ports, but whose basic operations are provided by user code. It has been lightly edited to fit R7RS style.


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