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(declare (type fixnum ---)) considered etc.

    Date: Wed, 23 Jul 86 14:58 EDT
    From: Daniel L. Weinreb <DLW@QUABBIN.SCRC.Symbolics.COM>

	Date: Wed, 23 Jul 86 12:32 EDT
	From: Guy Steele <gls@Think.COM>

	One thing one can say is (OR FIXNUM (SIGNED-BYTE 20)), say, which a
	sufficiently clever compiler (heh, heh, heh) would understand to mean
	"use a fixnum, unless fixnums are less than 20 bits, in which case use
	at least 20 bits (whatever that takes)".

    What is the advantage of using this instead of (SIGNED-BYTE 20)?

It feels more efficient.

Seriously, for declaring variables this probably buys you nothing.
I am guilty of somewhat fuzzy thinking.  However, in the case of an
implementation that packs structs, using this type for a component
would make some sense.  But I am reaching.