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/*
* Copyright (C) 2000, Imperial College
*
* This file is part of the Imperial College Exact Real Arithmetic Library.
* See the copyright notice included in the distribution for conditions
* of use.
*/
#include <stdio.h>
#include "real.h"
#include "real-impl.h"
/*
* For a real that has been forced to a stream (by force_R_Digs)
* this function retrieves the sign and the most significant digit information.
*/
void
retrieveInfo(Real x, Sign *sign, int *count, mpz_t digits)
{
Real derefToStrm(Real);
x = derefToStrm(x);
if (x == NULL)
Error(FATAL, E_INT, "retrieveInfo", "argument not forced");
if (x->gen.tag.type == SIGNX) {
*sign = x->signX.tag.value;
x = x->signX.x;
}
else
*sign = SPOS;
if ((x->gen.tag.type = DIGSX)) {
*count = x->digsX.count;
#ifdef PACK_DIGITS
if (*count <= DIGITS_PER_WORD)
mpz_set_si(digits, x->digsX.word.small);
else
#endif
mpz_set(digits, x->digsX.word.big);
}
else
Error(FATAL, E_INT, "retrieveInfo",
"no information has been forced from the argument");
}
/*
* Given a characteristic pair (c,n) where n is the number
* of digits recorded in c, this function returns the most significant
* digit yielding also (c', n-1)
*/
Digit
takeDigit(int *count, mpz_t digits)
{
Digit digit;
if (*count > 0)
mpz_tdiv_q_2exp(tmpa_z, digits, *count - 1);
if (mpz_cmp_ui(tmpa_z, 0) == 0)
digit = DZERO;
else
if (mpz_cmp_ui(tmpa_z, 1) == 0)
digit = DPOS;
else
if (mpz_cmp_si(tmpa_z, -1) == 0)
digit = DNEG;
else {
Error(FATAL, E_INT, "takeDigit",
"characteristic pair is not well formed");
digit = DZERO;
}
mpz_mul_2exp(tmpa_z, tmpa_z, *count - 1);
mpz_sub(digits, digits, tmpa_z);
*count = *count - 1;
return digit;
}
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