Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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kcc-5/lib/math/xmant.c
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/*
* +++ NAME +++
*
* XMANT Extract double precision number's mantissa
*
* +++ INDEX +++
*
* XMANT
* math libraries
* machine dependent routines
*
* +++ DESCRIPTION +++
*
* Extracts a double precision number's mantissa and returns it
* as a double precision number with a normalized mantissa and
* a zero exponent.
*
* +++ USAGE +++
*
* double _xmant(value)
* double value;
*
* +++ PROGRAMMER +++
*
* Fred Fish
* Goodyear Aerospace Corp, Arizona Div.
* (602) 932-7000 work
* (602) 894-6881 home
*
* +++ INTERNALS +++
*
* This routine is highly machine dependent. As such, no
* attempt was made to make it general, hence it may have
* to be completely rewritten when transportation of the
* floating point library is attempted.
*
* For the DECSYSTEM-20 the double precision word format is:
*
* WORD N => SEEEEEEEEMMMMMMMMMMMMMMMMMMMMMMMMMMM
* WORD N+1 => XMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
*
*/
#include "math.h"
#define MANT_MASK 0400777777777 /* Mantissa extraction mask */
#define ZPOS_MASK 0200000000000 /* Positive # zero exp mask */
#define ZNEG_MASK 0177000000000 /* Negative # zero exp mask */
double _xmant(value)
double value;
{
register int *vpntr;
if (value != 0.0) {
vpntr = (int *) &value;
*vpntr &= MANT_MASK;
if (value < 0.0)
*vpntr |= ZNEG_MASK;
else
*vpntr |= ZPOS_MASK;
}
return value;
}