| Date: Mon, 20 Feb 2012 01:07:09 -0800
 | From: Per Bothner <per@bothner.com>
 |
 | IEEE allows multiple NaN values.  They're unlikely to matter for
 | Scheme implementations or code, but I think a note is in order.
 |
 | I suggest something like the following:
 |
 | IEEE 754 specifies multiple NaN values.  A Scheme implementation
 | may collapse all NaN values to a single "representative NaN", or
 | there may be multiple NaN values.  In the latter case, the +nan.0
 | is the "canonical NaN" value.  Scheme functions in general must
 | treat all NaN values as equivalent. This specifically includes the
 | nan? functions, which must be true for all NaN values.  The only
 | standard Scheme function which can distingish different NaN values
 | is eqv?, though it is also permitted to treat all NaN values as
 | eqv?

EQ? is allowed to distinguish different NaN values.  It is better to
let EQ? make this distinction than EQV?.

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