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Merge pull request #8073 from berni44/rounding_f
std.format: Use rounding tool to round %f on floats.
This commit is contained in:
Razvan Nitu
GitHub
commit
16d01b0d14
1 changed files with 155 additions and 181 deletions
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@ -1493,7 +1493,7 @@ private void printFloatF(bool g, Writer, T, Char)(auto ref Writer w, T val,
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if (is(T == float) || is(T == double)
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|| (is(T == real) && (T.mant_dig == double.mant_dig || T.mant_dig == 64)))
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{
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import std.format.internal.write : writeAligned, PrecisionType;
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import std.format.internal.write : writeAligned, PrecisionType, RoundingClass, round;
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static if (!g)
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{
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@ -1510,9 +1510,7 @@ if (is(T == float) || is(T == double)
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char[T.max_exp + T.mant_dig + 1] dec_buf;
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// for rounding we need to know if the rest of the number is exactly 0, between 0 and 0.5, 0.5 or above 0.5
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enum roundType { ZERO, LOWER, FIVE, UPPER }
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roundType next;
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RoundingClass rc;
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// Depending on exp, we will use one of three algorithms:
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//
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@ -1630,7 +1628,7 @@ if (is(T == float) || is(T == double)
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dec_buf[--left] = cast(byte) ('0' + mod);
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}
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next = roundType.ZERO;
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rc = RoundingClass.ZERO;
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}
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else if (exp < small_bound)
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{
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@ -1713,9 +1711,9 @@ if (is(T == float) || is(T == double)
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static if (g) start = 2;
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if (lsu >= count - 1 && mybig[count - 1] == 0)
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next = roundType.ZERO;
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rc = RoundingClass.ZERO;
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else if (lsu == count - 1 && mybig[lsu] == 1L << 59)
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next = roundType.FIVE;
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rc = RoundingClass.FIVE;
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else
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{
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ulong over = 0;
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@ -1725,7 +1723,7 @@ if (is(T == float) || is(T == double)
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over = mybig[i] >> 60;
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mybig[i] &= (1L << 60) - 1;
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}
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next = over >= 5 ? roundType.UPPER : roundType.LOWER;
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rc = over >= 5 ? RoundingClass.UPPER : RoundingClass.LOWER;
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}
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}
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else
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@ -1805,7 +1803,7 @@ if (is(T == float) || is(T == double)
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static if (g) start = save_start;
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if (frac_part == 0)
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next = roundType.ZERO;
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rc = RoundingClass.ZERO;
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else
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{
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frac_part *= 10;
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@ -1813,73 +1811,15 @@ if (is(T == float) || is(T == double)
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frac_part &= ((1L << (T.mant_dig - 1 - exp)) - 1);
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if (nextDigit == 5 && frac_part == 0)
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next = roundType.FIVE;
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rc = RoundingClass.FIVE;
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else if (nextDigit >= 5)
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next = roundType.UPPER;
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rc = RoundingClass.UPPER;
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else
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next = roundType.LOWER;
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rc = RoundingClass.LOWER;
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}
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}
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// rounding
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bool roundUp = false;
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if (rm == RoundingMode.up)
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roundUp = next != roundType.ZERO && sgn != "-";
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else if (rm == RoundingMode.down)
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roundUp = next != roundType.ZERO && sgn == "-";
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else if (rm == RoundingMode.toZero)
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roundUp = false;
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else
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{
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assert(rm == RoundingMode.toNearestTiesToEven || rm == RoundingMode.toNearestTiesAwayFromZero,
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"RoundingMode is not toNearest");
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roundUp = next == roundType.UPPER;
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if (next == roundType.FIVE)
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{
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// IEEE754 allows for two different ways of implementing roundToNearest:
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// Round to nearest, ties away from zero
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if (rm == RoundingMode.toNearestTiesAwayFromZero)
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roundUp = true;
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else
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{
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// Round to nearest, ties to even
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auto last = dec_buf[right - 1];
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if (last == '.') last = dec_buf[right - 2];
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roundUp = last % 2 != 0;
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}
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}
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}
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if (roundUp)
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{
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foreach_reverse (i;left .. right)
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{
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if (dec_buf[i] == '.') continue;
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if (dec_buf[i] == '9')
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dec_buf[i] = '0';
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else
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{
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dec_buf[i]++;
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static if (g)
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{
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// in case of 0.0...009...9 => 0.0...010...0 we have to remove
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// the right most digit to get the precision right
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if (dec_buf[i] == '1')
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{
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foreach (j;left .. i)
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if (dec_buf[j] != '0' && dec_buf[j] != '.') goto printFloat_done;
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right--;
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}
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}
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goto printFloat_done;
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}
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}
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dec_buf[--left] = '1';
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printFloat_done:
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}
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if (round(dec_buf, left, right, rc, sgn == "-")) left--;
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while (right > start + 1 && dec_buf[right - 1] == '0') right--;
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@ -2018,11 +1958,20 @@ printFloat_done:
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@safe unittest
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{
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import std.math.hardware; // cannot be selective, because FloatingPointControl might not be defined
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// std.math's FloatingPointControl isn't available on all target platforms
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static if (is(FloatingPointControl))
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{
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FloatingPointControl fpctrl;
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auto f = FormatSpec!dchar("");
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f.spec = 'f';
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f.precision = 0;
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// ties away from zero
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fpctrl.rounding = FloatingPointControl.roundToNearest;
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/*
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assert(printFloat(11.5f, f, RoundingMode.toNearestTiesAwayFromZero) == "12");
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assert(printFloat(12.5f, f, RoundingMode.toNearestTiesAwayFromZero) == "13");
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assert(printFloat(11.7f, f, RoundingMode.toNearestTiesAwayFromZero) == "12");
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@ -2033,8 +1982,8 @@ printFloat_done:
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assert(printFloat(-11.7f, f, RoundingMode.toNearestTiesAwayFromZero) == "-12");
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assert(printFloat(-11.3f, f, RoundingMode.toNearestTiesAwayFromZero) == "-11");
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assert(printFloat(-11.0f, f, RoundingMode.toNearestTiesAwayFromZero) == "-11");
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*/
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// ties to even
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assert(printFloat(11.5f, f) == "12");
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assert(printFloat(12.5f, f) == "12");
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assert(printFloat(11.7f, f) == "12");
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@ -2046,6 +1995,8 @@ printFloat_done:
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assert(printFloat(-11.3f, f) == "-11");
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assert(printFloat(-11.0f, f) == "-11");
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fpctrl.rounding = FloatingPointControl.roundToZero;
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assert(printFloat(11.5f, f, RoundingMode.toZero) == "11");
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assert(printFloat(12.5f, f, RoundingMode.toZero) == "12");
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assert(printFloat(11.7f, f, RoundingMode.toZero) == "11");
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@ -2057,6 +2008,8 @@ printFloat_done:
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assert(printFloat(-11.3f, f, RoundingMode.toZero) == "-11");
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assert(printFloat(-11.0f, f, RoundingMode.toZero) == "-11");
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fpctrl.rounding = FloatingPointControl.roundUp;
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assert(printFloat(11.5f, f, RoundingMode.up) == "12");
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assert(printFloat(12.5f, f, RoundingMode.up) == "13");
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assert(printFloat(11.7f, f, RoundingMode.up) == "12");
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@ -2068,6 +2021,8 @@ printFloat_done:
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assert(printFloat(-11.3f, f, RoundingMode.up) == "-11");
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assert(printFloat(-11.0f, f, RoundingMode.up) == "-11");
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fpctrl.rounding = FloatingPointControl.roundDown;
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assert(printFloat(11.5f, f, RoundingMode.down) == "11");
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assert(printFloat(12.5f, f, RoundingMode.down) == "12");
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assert(printFloat(11.7f, f, RoundingMode.down) == "11");
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@ -2078,6 +2033,7 @@ printFloat_done:
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assert(printFloat(-11.7f, f, RoundingMode.down) == "-12");
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assert(printFloat(-11.3f, f, RoundingMode.down) == "-12");
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assert(printFloat(-11.0f, f, RoundingMode.down) == "-11");
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}
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}
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@safe unittest
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@ -2563,11 +2519,21 @@ if (is(T == float) || is(T == double)
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@safe unittest
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{
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import std.math.hardware; // cannot be selective, because FloatingPointControl might not be defined
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// std.math's FloatingPointControl isn't available on all target platforms
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static if (is(FloatingPointControl))
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{
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FloatingPointControl fpctrl;
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char[256] buf;
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auto f = FormatSpec!dchar("");
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f.spec = 'g';
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f.precision = 2;
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fpctrl.rounding = FloatingPointControl.roundToNearest;
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/*
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assert(printFloat(11.5f, f, RoundingMode.toNearestTiesAwayFromZero) == "12");
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assert(printFloat(12.5f, f, RoundingMode.toNearestTiesAwayFromZero) == "13");
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assert(printFloat(11.7f, f, RoundingMode.toNearestTiesAwayFromZero) == "12");
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@ -2578,6 +2544,7 @@ if (is(T == float) || is(T == double)
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assert(printFloat(-11.7f, f, RoundingMode.toNearestTiesAwayFromZero) == "-12");
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assert(printFloat(-11.3f, f, RoundingMode.toNearestTiesAwayFromZero) == "-11");
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assert(printFloat(-11.0f, f, RoundingMode.toNearestTiesAwayFromZero) == "-11");
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*/
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// ties to even
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assert(printFloat(11.5f, f) == "12");
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@ -2591,6 +2558,8 @@ if (is(T == float) || is(T == double)
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assert(printFloat(-11.3f, f) == "-11");
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assert(printFloat(-11.0f, f) == "-11");
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fpctrl.rounding = FloatingPointControl.roundToZero;
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assert(printFloat(11.5f, f, RoundingMode.toZero) == "11");
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assert(printFloat(12.5f, f, RoundingMode.toZero) == "12");
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assert(printFloat(11.7f, f, RoundingMode.toZero) == "11");
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@ -2602,6 +2571,8 @@ if (is(T == float) || is(T == double)
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assert(printFloat(-11.3f, f, RoundingMode.toZero) == "-11");
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assert(printFloat(-11.0f, f, RoundingMode.toZero) == "-11");
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fpctrl.rounding = FloatingPointControl.roundUp;
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assert(printFloat(11.5f, f, RoundingMode.up) == "12");
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assert(printFloat(12.5f, f, RoundingMode.up) == "13");
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assert(printFloat(11.7f, f, RoundingMode.up) == "12");
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@ -2613,6 +2584,8 @@ if (is(T == float) || is(T == double)
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assert(printFloat(-11.3f, f, RoundingMode.up) == "-11");
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assert(printFloat(-11.0f, f, RoundingMode.up) == "-11");
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fpctrl.rounding = FloatingPointControl.roundDown;
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assert(printFloat(11.5f, f, RoundingMode.down) == "11");
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assert(printFloat(12.5f, f, RoundingMode.down) == "12");
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assert(printFloat(11.7f, f, RoundingMode.down) == "11");
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@ -2623,6 +2596,7 @@ if (is(T == float) || is(T == double)
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assert(printFloat(-11.7f, f, RoundingMode.down) == "-12");
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assert(printFloat(-11.3f, f, RoundingMode.down) == "-12");
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assert(printFloat(-11.0f, f, RoundingMode.down) == "-11");
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}
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}
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@safe unittest
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