There's an issue about the sample implementation that I don't know how to resolve.  The flonum procedures that are semantically the same as generic procedures, like flsin, can be portably implemented just using sin.  But the ones that come from the <math.h> library can't be, or at least not without ignoring the accuracy constraints.  Every implementer has access to the C library, but that doesn't mean every Scheme implementation provides access to it for their users, and if they do, it will be in a very implementation-specific way, as there is no standard FFI.

What's the Right Thing to do here?  Provide portable but inexact implementations, or just say that the implementation is inherently specific to a given Scheme?

I'm especially interested in Art's comments, but anyone else's too.

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