From the Gambit web page:

The Gambit Scheme system is a complete, portable, efficient and reliable implementation of the Scheme programming language.

To reproduce my results on Ubuntu Gutsy Gibbon, install Gambit with

sudo apt-get install gambc

and run the interpreter with

gsi -:s,daq-1,h10000 2>&1

Gambit makes the following choices:

- Complies with the R5RS letrec specification even if the expressions being bound return more than once (via capturing and reentering their continuations). (more)
- Does not provide the 'syntax-rules' macro system. (more)
- Allows forcing non-promises. (more)
- Allows the 'sqrt' procedure to return exact results when able. (more)
- Allows the '*' procedure to return exact zero when a factor is an exact zero, even if other factors are inexact. (more)
- Allows the '/' procedure to return exact zero when the dividend is an exact zero, even if some divisors are inexact. (more)
- Allows division by inexact zero. (more)
- Supports arbitrary precision literal integers. (more)
- Supports arbitrary precision computed integers. (more)
- Supports the literal syntax for rational numbers (e.g. 1/2 is the literal number one half). (more)
- Supports the literal syntax for complex numbers (e.g. 1+i is the complex number with real and imaginary parts both 1). (more)
- Supports nontrivial exact rational numbers (e.g. (/ 1 3) produces an exact one third, not a floating point approximation). (more)
- Supports nontrivial exact complex numbers. (more)
- Requires 'real?' numbers to have exact zero imaginary part (e.g. (not (real? 0+0.0i)) is true) (more)
- Guesses the denominators of inexact numbers per R5RS. (more)