CLIM mail archive


Re: reducing time overhead of text display (in 1.1)

   Date: Wed, 22 Dec 1993 14:34 -0500
   From: Scott McKay <SWM@STONY-BROOK.SCRC.Symbolics.COM>

       Date: Wed, 22 Dec 1993 14:25 EST

	  Date: Wed, 22 Dec 1993 13:27 -0500
	  From: Scott McKay <>

	  Believe it or not, CLIM has a compile-time conditional that allows the
	  CLIM implementor to choose between three types of coordinates: T,
	  SINGLE-FLOAT, and FIXNUM.  Right now, CLIM uses T.  T and SINGLE-FLOAT
	  work equally well in Genera, but CER and I verified that using
	  SINGLE-FLOAT is a dog under Allero (and probably Lucid, too) because it
	  guarantees that you have to cons, whereas when CLIM uses T, CLIM often
	  manages to use fixnums.  CLIM 1.1 always used FIXNUM, but I never quite
	  finished debugging the FIXNUM case in CLIM 2.0.

       Some implementations have a SHORT-FLOAT that doesn't cons.  Perhaps
       CLIM could use SHORT-FLOAT internally whenever it's available.

   The range of SHORT-FLOAT is allowed to be too small for some things.

Portably speaking, that is true.  Page 20 of CLtL2 says that a
SHORT-FLOAT could have an exponent of only 5 bits (i.e., exponents up
to about +16, and hence values up to about +6s4).  But since you were
speaking of a compile-time conditional anyway, I was suggesting that a
CL implementation that has non-consing SHORT-FLOATs with, for example,
8-bit exponents (i.e., exponents up to about +128, and hence values up
to about +3s38) might wish to use SHORT-FLOAT internally in CLIM.

        Lawrence G. Mayka
        AT&T Bell Laboratories

Standard disclaimer.


Main Index | Thread Index