We are planning a simple SRFI to mae floats from integers (or from strings), since that's useful when parsing any kind of text syntax that has real numbers. The details are implementation-dependent and tricky to get right.
Here's the spec we have so far: https://github.com/pre-srfi/make-float
The API is:
(inexact-real-from-strings int frac precision exp) -> real (inexact-real-from-integers int frac frac-length precision exp) -> real
Example usage:
(inexact-real-from-strings "-123" "45" 'e "6") ; => -123.45e6 (inexact-real-from-integers -123 45 2 'e 6) ; => -123.45e6
The 2 in the last example means two decimal places. It's needed to disambiguate between .6 .06 .006 .0006 etc.
There are both math and Scheme wizards on this list. Could someone verify whether this is a sane design before we submit the SRFI draft? It's been ok'd by one mathematician already so I'm hopeful :)
There's also an inverse API to serve as a backend for string formatting packages:
(strings-from-inexact-real real frac-length) -> int; frac; exp (integers-from-inexact-real real frac-length) -> int; frac; exp