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Re: reading NaNs
Aubrey Jaffer wrote:
Are you suggesting a single NaN or multiple distinct NaNs?
To support existing IEEE-754 hardware, R6RS must not mandate multiple
distinct NaNs. But specifying a singular NaN prevents implementations
from fully supporting IEEE-754 in the future.
All hardware should recognize all NaNs. Therefore, allowing NaNs to be
generated with aribitrary bit patterns is not a problem. However,
different hardware need not generate the same NaNs for identical operands.
However, I still think we need a read syntax. Suppose program A
calculates a value and writes it to a file and program B reads the value
from the file and uses it. Is is not useful for program A to be able to
communicate to program B that it got a NaN? This would suggest we need a
write syntax and a read syntax for NaNs. (Whether this syntax should
specify and preserve the bit patterns is another argument.)
Dr Alan Watson
Centro de Radioastronomía y Astrofísica
Universidad Astronómico Nacional de México