Would 'gtransduce' be a good name (to match the ones in SRFI 158)?

> Indeed.   I have a small pre-SRFI at <
> https://bitbucket.org/cowan/r7rs-wg1-infra/src/default/PortOperationsCowan.md>,
> the first half of which is about mapping between SRFI 158 generators and
> accumulators and Scheme ports.

Your input-port->generator and output-port->accumulator procedures also
don't require a port :)