This page is part of the web mail archives of SRFI 70 from before July 7th, 2015. The new archives for SRFI 70 contain all messages, not just those from before July 7th, 2015.
I know that it's not the right thing in all cases and all times, but I think it's a good thing in most of the cases I use, for an operation on exact arguments whose mathematically correct result is too large to be represented as an exact number, to (silently) return an inexact number of the highest available precision. Thus, precision escalating out of control in an iterative algorithm using rationals eventually breaks a point where the denominator is more than three hundred digits long, and instead of crashing or bogging down with ever-larger diophantine fractional calculations, and an addition or a multiplication or whatever returns a float. This behavior is neither mandated nor forbidden by R5RS. I think that's a good thing. Your proposal also does not mandate nor forbid it; I think that's a good thing too. But it sounds like you came really close to forbidding it, and may have failed to do so only by accident. So I just wanted to point it out as a frequently desirable behavior. Bear