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Merge pull request #8059 from berni44/rounding_a

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std.format: Use rounding tool to round %a on floats.
This commit is contained in:
Razvan Nitu 2021-05-13 14:35:19 +08:00 • committed by GitHub
commit dba3cbc88c
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2 changed files with 95 additions and 125 deletions
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112
std/format/internal/floats.d
View file

@ -104,7 +104,7 @@ if (is(T == float) || is(T == double)
} }
// save integer part // save integer part
char[1] first = '0' + ((mnt >> (T.mant_dig - 1)) & 1); char first = '0' + ((mnt >> (T.mant_dig - 1)) & 1);
mnt &= (1L << (T.mant_dig - 1)) - 1; mnt &= (1L << (T.mant_dig - 1)) - 1;
static if (is(T == float) || (is(T == real) && T.mant_dig == 64)) static if (is(T == float) || (is(T == real) && T.mant_dig == 64))
@ -117,8 +117,8 @@ if (is(T == float) || is(T == double)
static assert(mant_len % 4 == 0, "mantissa with wrong length"); static assert(mant_len % 4 == 0, "mantissa with wrong length");
// print full mantissa // print full mantissa
char[(mant_len - 1) / 4 + 2] hex_mant; char[(mant_len - 1) / 4 + 3] hex_mant;
size_t hex_mant_pos = 1; size_t hex_mant_pos = 2;
size_t pos = mant_len; size_t pos = mant_len;
auto gap = 39 - 32 * is_upper; auto gap = 39 - 32 * is_upper;
@ -131,10 +131,11 @@ if (is(T == float) || is(T == double)
// has been replaced with an expression without branches, doing the same // has been replaced with an expression without branches, doing the same
hex_mant[hex_mant_pos++] = cast(char) (tmp + gap * ((tmp + 6) >> 4) + '0'); hex_mant[hex_mant_pos++] = cast(char) (tmp + gap * ((tmp + 6) >> 4) + '0');
} }
hex_mant[0] = '.'; hex_mant[0] = first;
hex_mant[1] = '.';
if (f.precision == f.UNSPECIFIED) if (f.precision == f.UNSPECIFIED)
f.precision = cast(int) hex_mant_pos - 1; f.precision = cast(int) hex_mant_pos - 2;
auto exp_sgn = exp >= 0 ? '+' : '-'; auto exp_sgn = exp >= 0 ? '+' : '-';
if (exp < 0) exp = -exp; if (exp < 0) exp = -exp;
@ -158,88 +159,39 @@ if (is(T == float) || is(T == double)
exp_str[--exp_pos] = exp_sgn; exp_str[--exp_pos] = exp_sgn;
exp_str[--exp_pos] = is_upper ? 'P' : 'p'; exp_str[--exp_pos] = is_upper ? 'P' : 'p';
if (f.precision < hex_mant_pos - 1) if (f.precision < hex_mant_pos - 2)
{ {
enum roundType { ZERO, LOWER, FIVE, UPPER } import std.format.internal.write : RoundingClass, round;
roundType next;
if (hex_mant[f.precision + 1] == '0') RoundingClass rc;
next = roundType.ZERO;
else if (hex_mant[f.precision + 1] < '8') if (hex_mant[f.precision + 2] == '0')
next = roundType.LOWER; rc = RoundingClass.ZERO;
else if (hex_mant[f.precision + 1] > '8') else if (hex_mant[f.precision + 2] < '8')
next = roundType.UPPER; rc = RoundingClass.LOWER;
else if (hex_mant[f.precision + 2] > '8')
rc = RoundingClass.UPPER;
else else
next = roundType.FIVE; rc = RoundingClass.FIVE;
if (next == roundType.ZERO || next == roundType.FIVE) if (rc == RoundingClass.ZERO || rc == RoundingClass.FIVE)
{ {
foreach (i;f.precision + 2 .. hex_mant_pos) foreach (i;f.precision + 3 .. hex_mant_pos)
{ {
if (hex_mant[i] > '0') if (hex_mant[i] > '0')
{ {
next = next == roundType.ZERO ? roundType.LOWER : roundType.UPPER; rc = rc == RoundingClass.ZERO ? RoundingClass.LOWER : RoundingClass.UPPER;
break; break;
} }
} }
} }
bool roundUp = false; hex_mant_pos = f.precision + 2;
if (rm == RoundingMode.up) round(hex_mant, 0, hex_mant_pos, rc, sgn == "-", is_upper ? 'F' : 'f');
roundUp = next != roundType.ZERO && sgn != "-";
else if (rm == RoundingMode.down)
roundUp = next != roundType.ZERO && sgn == "-";
else if (rm == RoundingMode.toZero)
roundUp = false;
else
{
assert(rm == RoundingMode.toNearestTiesToEven || rm == RoundingMode.toNearestTiesAwayFromZero,
"RoundingMode is not toNearest");
roundUp = next == roundType.UPPER;
if (next == roundType.FIVE)
{
// IEEE754 allows for two different ways of implementing roundToNearest:
// Round to nearest, ties away from zero
if (rm == RoundingMode.toNearestTiesAwayFromZero)
roundUp = true;
else
{
// Round to nearest, ties to even
auto last = f.precision == 0 ? first[0] : hex_mant[f.precision];
roundUp = (last <= '9' && last % 2 != 0) || (last >= '9' && last % 2 == 0);
}
}
} }
hex_mant_pos = f.precision + 1; writeAligned(w, prefix[1 - sgn.length .. $], hex_mant[0 .. 1], hex_mant[1 .. hex_mant_pos],
if (roundUp)
{
foreach_reverse (i;0 .. hex_mant_pos)
{
if (hex_mant[i] == '.')
{
first[0]++;
break;
}
if (hex_mant[i] == 'f' || hex_mant[i] == 'F')
hex_mant[i] = '0';
else
{
if (hex_mant[i] == '9')
hex_mant[i] = is_upper ? 'A' : 'a';
else
hex_mant[i]++;
break;
}
}
}
}
writeAligned(w, prefix[1 - sgn.length .. $], first[], hex_mant[0 .. hex_mant_pos],
exp_str[exp_pos .. $], f, PrecisionType.fractionalDigits); exp_str[exp_pos .. $], f, PrecisionType.fractionalDigits);
} }
@ -532,10 +484,20 @@ if (is(T == float) || is(T == double)
@safe unittest @safe unittest
{ {
import std.math.hardware; // cannot be selective, because FloatingPointControl might not be defined
// std.math's FloatingPointControl isn't available on all target platforms
static if (is(FloatingPointControl))
{
FloatingPointControl fpctrl;
auto f = FormatSpec!dchar(""); auto f = FormatSpec!dchar("");
f.spec = 'a'; f.spec = 'a';
f.precision = 1; f.precision = 1;
fpctrl.rounding = FloatingPointControl.roundToNearest;
/* tiesAwayFromZero currently not supported
assert(printFloat(0x1.18p0, f, RoundingMode.toNearestTiesAwayFromZero) == "0x1.2p+0"); assert(printFloat(0x1.18p0, f, RoundingMode.toNearestTiesAwayFromZero) == "0x1.2p+0");
assert(printFloat(0x1.28p0, f, RoundingMode.toNearestTiesAwayFromZero) == "0x1.3p+0"); assert(printFloat(0x1.28p0, f, RoundingMode.toNearestTiesAwayFromZero) == "0x1.3p+0");
assert(printFloat(0x1.1ap0, f, RoundingMode.toNearestTiesAwayFromZero) == "0x1.2p+0"); assert(printFloat(0x1.1ap0, f, RoundingMode.toNearestTiesAwayFromZero) == "0x1.2p+0");
@ -546,6 +508,7 @@ if (is(T == float) || is(T == double)
assert(printFloat(-0x1.1ap0, f, RoundingMode.toNearestTiesAwayFromZero) == "-0x1.2p+0"); assert(printFloat(-0x1.1ap0, f, RoundingMode.toNearestTiesAwayFromZero) == "-0x1.2p+0");
assert(printFloat(-0x1.16p0, f, RoundingMode.toNearestTiesAwayFromZero) == "-0x1.1p+0"); assert(printFloat(-0x1.16p0, f, RoundingMode.toNearestTiesAwayFromZero) == "-0x1.1p+0");
assert(printFloat(-0x1.10p0, f, RoundingMode.toNearestTiesAwayFromZero) == "-0x1.1p+0"); assert(printFloat(-0x1.10p0, f, RoundingMode.toNearestTiesAwayFromZero) == "-0x1.1p+0");
*/
assert(printFloat(0x1.18p0, f) == "0x1.2p+0"); assert(printFloat(0x1.18p0, f) == "0x1.2p+0");
assert(printFloat(0x1.28p0, f) == "0x1.2p+0"); assert(printFloat(0x1.28p0, f) == "0x1.2p+0");
@ -558,6 +521,8 @@ if (is(T == float) || is(T == double)
assert(printFloat(-0x1.16p0, f) == "-0x1.1p+0"); assert(printFloat(-0x1.16p0, f) == "-0x1.1p+0");
assert(printFloat(-0x1.10p0, f) == "-0x1.1p+0"); assert(printFloat(-0x1.10p0, f) == "-0x1.1p+0");
fpctrl.rounding = FloatingPointControl.roundToZero;
assert(printFloat(0x1.18p0, f, RoundingMode.toZero) == "0x1.1p+0"); assert(printFloat(0x1.18p0, f, RoundingMode.toZero) == "0x1.1p+0");
assert(printFloat(0x1.28p0, f, RoundingMode.toZero) == "0x1.2p+0"); assert(printFloat(0x1.28p0, f, RoundingMode.toZero) == "0x1.2p+0");
assert(printFloat(0x1.1ap0, f, RoundingMode.toZero) == "0x1.1p+0"); assert(printFloat(0x1.1ap0, f, RoundingMode.toZero) == "0x1.1p+0");
@ -569,6 +534,8 @@ if (is(T == float) || is(T == double)
assert(printFloat(-0x1.16p0, f, RoundingMode.toZero) == "-0x1.1p+0"); assert(printFloat(-0x1.16p0, f, RoundingMode.toZero) == "-0x1.1p+0");
assert(printFloat(-0x1.10p0, f, RoundingMode.toZero) == "-0x1.1p+0"); assert(printFloat(-0x1.10p0, f, RoundingMode.toZero) == "-0x1.1p+0");
fpctrl.rounding = FloatingPointControl.roundUp;
assert(printFloat(0x1.18p0, f, RoundingMode.up) == "0x1.2p+0"); assert(printFloat(0x1.18p0, f, RoundingMode.up) == "0x1.2p+0");
assert(printFloat(0x1.28p0, f, RoundingMode.up) == "0x1.3p+0"); assert(printFloat(0x1.28p0, f, RoundingMode.up) == "0x1.3p+0");
assert(printFloat(0x1.1ap0, f, RoundingMode.up) == "0x1.2p+0"); assert(printFloat(0x1.1ap0, f, RoundingMode.up) == "0x1.2p+0");
@ -580,6 +547,8 @@ if (is(T == float) || is(T == double)
assert(printFloat(-0x1.16p0, f, RoundingMode.up) == "-0x1.1p+0"); assert(printFloat(-0x1.16p0, f, RoundingMode.up) == "-0x1.1p+0");
assert(printFloat(-0x1.10p0, f, RoundingMode.up) == "-0x1.1p+0"); assert(printFloat(-0x1.10p0, f, RoundingMode.up) == "-0x1.1p+0");
fpctrl.rounding = FloatingPointControl.roundDown;
assert(printFloat(0x1.18p0, f, RoundingMode.down) == "0x1.1p+0"); assert(printFloat(0x1.18p0, f, RoundingMode.down) == "0x1.1p+0");
assert(printFloat(0x1.28p0, f, RoundingMode.down) == "0x1.2p+0"); assert(printFloat(0x1.28p0, f, RoundingMode.down) == "0x1.2p+0");
assert(printFloat(0x1.1ap0, f, RoundingMode.down) == "0x1.1p+0"); assert(printFloat(0x1.1ap0, f, RoundingMode.down) == "0x1.1p+0");
@ -591,6 +560,7 @@ if (is(T == float) || is(T == double)
assert(printFloat(-0x1.16p0, f, RoundingMode.down) == "-0x1.2p+0"); assert(printFloat(-0x1.16p0, f, RoundingMode.down) == "-0x1.2p+0");
assert(printFloat(-0x1.10p0, f, RoundingMode.down) == "-0x1.1p+0"); assert(printFloat(-0x1.10p0, f, RoundingMode.down) == "-0x1.1p+0");
} }
}
// for 100% coverage // for 100% coverage
@safe unittest @safe unittest

2
std/format/internal/write.d
View file

@ -3693,7 +3693,7 @@ private long getWidth(T)(T s)
enum RoundingClass { ZERO, LOWER, FIVE, UPPER } enum RoundingClass { ZERO, LOWER, FIVE, UPPER }
bool round(T)(ref T sequence, size_t left, size_t right, RoundingClass type, bool negative, char max = '9') bool round(T)(ref T sequence, size_t left, size_t right, RoundingClass type, bool negative, char max = '9')
in (left > 0) // != 0 because we might need one carry in (left >= 0) // should be left > 0, but if you know ahead, that there's no carry, left == 0 is fine
in (left < sequence.length) in (left < sequence.length)
in (right >= 0) in (right >= 0)
in (right <= sequence.length) in (right <= sequence.length)