This is solved by the Scheme numerical tower, which prefers exact representation​s (including exact rationals) unless inexact representation is explicitly requested or forced by an operation that doesn't support exact results.
The problem is remembering to only input rationals :) So instead of doing (iota 100 0.1 0.1), you do (iota 100 (/ 1 10) (/ 1 10)). That does not work in chicken for some reason.
I don't know if precomputation is ever guaranteed for those things, but otherwise it would be neat to be able to input rationals directly into the source.
Edit: So, this is scheme standard discovery week: apparently inputing 1/10 works just fine. I can't believe I missed this.
