- fl-fast-fl+*constant
Bound to #t if (fl+* x y z) executes about as fast as, or faster than, (fl+ (fl* x y) z); bound to #f otherwise. (C99 FP_FAST_FMA)
So that the value of this variable can be determined at compile time, R7RS implementations and other implementations that provide a features function should provide the feature fl-fast-fl+* if this variable is true, and not if it is false or the value is unknown at compile time.