Initial revision
This commit is contained in:
ceriel
213
mach/proto/fp/compact.c
Normal file
213
mach/proto/fp/compact.c
Normal file
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/*
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#define PRT_EXIT
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#define PRT_TRAP
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#define PRT_ENTRY
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COMPACT EXTEND FORMAT INTO FLOAT OF PROPER SIZE
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*/
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# include "FP_bias.h"
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# include "FP_shift.h"
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# include "FP_trap.h"
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# include "FP_types.h"
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# include "get_put.h"
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compact(f,to,size)
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EXTEND *f;
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_double *to;
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int size;
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{
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DOUBLE *DBL;
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int error = 0;
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SINGLE *SGL;
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int exact;
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#ifdef PRT_ENTRY
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prt_ext("enter compact:",f);
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#endif PRT_ENTRY
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if (size == sizeof(_double))
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/********************************************************/
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/*
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COMPACT EXTENDED INTO DOUBLE
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*/
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/********************************************************/
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{
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if ((f->m1|(f->m2 & DBL_ZERO)) == 0L) {
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zrf8(to);
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goto leave;
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}
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f->exp += DBL_BIAS; /* restore proper bias */
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if (f->exp > DBL_MAX) {
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dbl_over: trap(EFOVFL);
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#ifdef PRT_TRAP
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prt_ext("FCOMPACT DBL OVERFLOW",f);
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#endif PRT_TRAP
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f->exp = DBL_MAX;
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f->m1 = f->m2 = 0L;
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if (error++)
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return;
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}
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else if (f->exp < DBL_MIN) {
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#ifdef PRT_TRAP
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prt_ext("FCOMPACT DBL UNDERFLOW",f);
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#endif PRT_TRAP
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trap(EFUNFL);
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f->exp = DBL_MIN;
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f->m1 = f->m2 = 0L;
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if (error++)
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return;
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}
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/* local CAST conversion */
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DBL = (DOUBLE *) to;
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/* check if answer is exact */
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/* (the last 11 bits are zero (0) */
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exact = ((f->m2 & DBL_EXACT) == 0) ? 1 : 0;
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/* because of special format shift only 10 bits */
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/* bit shift mantissa 10 bits */
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/* first align within words, then do store operation */
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DBL->_s.p1.fract = f->m1 >> DBL_RUNPACK; /* plus 22 == 32 */
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DBL->_s.p2 = f->m2 >> DBL_RUNPACK; /* plus 22 == 32 */
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DBL->_s.p2 |= (f->m1 << DBL_LUNPACK); /* plus 10 == 32 */
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/* if not exact then round to nearest */
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if (!exact) {
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/* INEXACT(); */
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if (f->m2 & DBL_ROUNDUP) {
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DBL->_s.p2++; /* rounding up */
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if (DBL->_s.p2 == 0L) { /* carry out */
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#ifdef PRT_RNDMSG
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write(2,"rounding up lsb\n",16);
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#endif PRT_RNDMSG
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DBL->_s.p1.fract++;
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if (DBL->_s.p1.fract & DBL_CARRYOUT) { /* carry out */
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#ifdef PRT_RNDMSG
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write(2,"shift due to rounding\n",22);
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#endif PRT_RNDMSG
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if (DBL->_s.p1.fract & 01)
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DBL->_s.p2 = CARRYBIT;
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DBL->_s.p1.fract >>= 1;
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f->exp++;
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}
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}
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}
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}
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/* check for overflow */
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if (f->exp >= DBL_MAX)
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goto dbl_over;
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/* STORE EXPONENT: */
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/* 1) clear leading bits (B4-B15) */
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DBL->_s.p1.fract &= DBL_MASK;
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/* 2) shift and store exponent */
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f->exp <<= DBL_EXPSHIFT;
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DBL->_s.p1.fract |= ((long) f->exp << EXP_STORE);
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}
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else
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/********************************************************/
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/*
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COMPACT EXTENDED INTO FLOAT
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*/
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/********************************************************/
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{
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/* local CAST conversion */
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SGL = (SINGLE *) to;
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if ((f->m1 & SGL_ZERO) == 0L) {
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SGL->fract = 0L;
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goto leave;
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}
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f->exp += SGL_BIAS; /* restore bias */
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if (f->exp > SGL_MAX) {
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sgl_over: trap(EFOVFL);
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#ifdef PRT_TRAP
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prt_ext("FCOMPACT FLOAT OVERFLOW",f);
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#endif PRT_TRAP
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f->exp = SGL_MAX;
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f->m1 = f->m2 = 0L;
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if (error++)
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return;
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}
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else if (f->exp < SGL_MIN) {
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#ifdef PRT_TRAP
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prt_ext("FCOMPACT FLOAT UNDERFLOW",f);
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#endif PRT_TRAP
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trap(EFUNFL);
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f->exp = SGL_MIN;
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f->m1 = f->m2 = 0L;
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if (error++)
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return;
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}
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/* check if the answer is exact */
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/* the last 40 bits are zero */
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/* check first last bits of mantissa 1 */
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exact = ((f->m1 & SGL_EXACT) == 0) ? 1 : 0;
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/* check last 32 bits in mantissa 2 */
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if (exact) /* first part masks to zero */
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exact = (f->m2 == 0L) ? 1 : 0;
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/* shift mantissa and store */
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SGL->fract = (f->m1 >> SGL_RUNPACK);
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/* check for rounding to nearest */
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if (!exact) {
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/* INEXACT(); */
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if (f->m1 & SGL_ROUNDUP) {
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SGL->fract++;
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#ifdef PRT_RNDMSG
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write(2,"rounding up lsb\n",16);
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#endif PRT_RNDMSG
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/* check normal */
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if (SGL->fract & SGL_CARRYOUT) {
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SGL->fract >>= 1;
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f->exp++;
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}
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}
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}
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if (f->exp >= SGL_MAX)
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goto sgl_over;
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/* STORE EXPONENT */
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/* 1) clear leading bit of fraction */
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SGL->fract &= SGL_MASK; /* B23-B31 are 0 */
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/* 2) shift and store exponent */
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f->exp <<= SGL_EXPSHIFT;
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SGL->fract |= ((long) f->exp << EXP_STORE);
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}
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/********************************************************/
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/*
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STORE SIGN BIT
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*/
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/********************************************************/
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if (f->sign) {
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SGL = (SINGLE *) to; /* make sure */
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SGL->fract |= CARRYBIT;
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}
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/********************************************************/
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/*
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STORE MANTISSA
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/*
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/********************************************************/
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if (size == sizeof(_double)) {
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put4(DBL->_s.p1.fract, (char *) &DBL->_s.p1.fract);
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put4(DBL->_s.p2, (char *) &DBL->_s.p2);
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}
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else
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put4(SGL->fract, (char *) &SGL->fract);
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leave:
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#ifdef PRT_EXIT
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prt_ext("exit compact:",f);
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prt_dbl((DOUBLE *) to,size); getchar();
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#endif PRT_EXIT
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; /* end of print statement or null statement */
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}
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