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MPREAL_HAVE_DYNAMIC_STD_NUMERIC_LIMITS -> MPREAL_FIXED_PRECISION #28

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MPREAL_HAVE_DYNAMIC_STD_NUMERIC_LIMITS -> MPREAL_FIXED_PRECISION #28

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MPREAL_HAVE_DYNAMIC_STD_NUMERIC_LIMITS -> MPREAL_FIXED_PRECISION
cffk Jan 25, 2025
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Merge branch 'master' into fixed-precision
cffk Aug 1, 2025
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36 changes: 19 additions & 17 deletions mpreal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -63,10 +63,15 @@

// Options
#define MPREAL_HAVE_MSVC_DEBUGVIEW // Enable Debugger Visualizer for "Debug" builds in MSVC.
#ifndef MPREAL_HAVE_DYNAMIC_STD_NUMERIC_LIMITS
#define MPREAL_HAVE_DYNAMIC_STD_NUMERIC_LIMITS 1 // Enable extended std::numeric_limits<mpfr::mpreal> specialization.
// Meaning that "digits", "round_style" and similar members are defined as functions, not constants.
// See std::numeric_limits<mpfr::mpreal> at the end of the file for more information.
#ifndef MPREAL_FIXED_PRECISION
// If MPREAL_FIXED_PRECISION == 0 (the default), then enable extended
// std::numeric_limits<mpfr::mpreal> specialization. Meaning that "digits", "round_style" and
// similar members are defined as functions, not constants. See std::numeric_limits<mpfr::mpreal>
// at the end of the file for more information.
//
// Otherwise, digits returns the value MPREAL_FIXED_PRECISION which acts as compile-time setting for
// the precision provided that set_default_prec is called with this precision.
#define MPREAL_FIXED_PRECISION 0
#endif

// Library version
Expand Down Expand Up @@ -3324,7 +3329,7 @@ namespace std
MPREAL_PERMISSIVE_EXPR static const int min_exponent10 = (int) (MPFR_EMIN_DEFAULT * 0.3010299956639811);
MPREAL_PERMISSIVE_EXPR static const int max_exponent10 = (int) (MPFR_EMAX_DEFAULT * 0.3010299956639811);

#if MPREAL_HAVE_DYNAMIC_STD_NUMERIC_LIMITS
#if MPREAL_FIXED_PRECISION == 0

// Following members should be constant according to standard, but they can be variable in MPFR
// So we define them as functions here.
Expand Down Expand Up @@ -3367,20 +3372,17 @@ namespace std
// Digits and round_style are NOT constants when it comes to mpreal.
// If possible, please use functions digits() and round_style() defined above.
//
// These (default) values are preserved for compatibility with existing libraries, e.g. boost.
// Change them accordingly to your application.
//
// For example, if you use 256 bits of precision uniformly in your program, then:
// digits = 256
// digits10 = 77
// max_digits10 = 78
//
// Approximate formula for decimal digits is: digits10 = floor(log10(2) * digits). See bits2digits() for more details.
// However if constant values for digits are required , e.g., for use with boost, the
// precision can be set at compile time with a positive value for MPREAL_FIXED_PRECISION.
// This value is used for "digits" (and hence also for "digits10" and "max_digits10"). It's
// advisable to call set_default_prec with this precision so that everything is consistent.

static const std::float_round_style round_style = round_to_nearest;
static const int digits = 53;
static const int digits10 = 15;
static const int max_digits10 = 16;
static const int digits = MPREAL_FIXED_PRECISION;
// 4004/13301 = log10(2) + 2e-9, so this is approximately equivalent to
// digits10 = mpfr::bits2digits(digits);
static const int digits10 = (4004 * digits) / 13301;
static const int max_digits10 = digits10 + 1;
#endif
};

Expand Down