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merged 1 commit into from
Dec 16, 2020
Merged

human friendly fp spec #325

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162 changes: 97 additions & 65 deletions source/mir/bignum/decimal.d
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ import std.traits: isSomeChar;
public import mir.bignum.low_level_view: DecimalExponentKey;
import mir.bignum.low_level_view: ceilLog10Exp2;

private enum expBufferShift = 2 + ceilLog10Exp2(size_t.sizeof * 8);
private enum expBufferLength = 2 + ceilLog10Exp2(size_t.sizeof * 8);

/++
Stack-allocated decimal type.
Expand All @@ -22,6 +22,7 @@ Params:
struct Decimal(size_t maxSize64)
if (maxSize64 && maxSize64 <= ushort.max)
{
import mir.format: NumericSpec;
import mir.bignum.integer;
import mir.bignum.low_level_view;
import std.traits: isMutable, isFloatingPoint;
Expand Down Expand Up @@ -183,21 +184,50 @@ struct Decimal(size_t maxSize64)
assert(!decimal.fromStringImpl("0d", key));
}

private enum eDecimalLength = 2 + ceilLog10Exp2(coefficient.data.length * (size_t.sizeof * 8)) + expBufferShift;
private enum coefficientBufferLength = 2 + ceilLog10Exp2(coefficient.data.length * (size_t.sizeof * 8)); // including dot and sign
private enum eDecimalLength = coefficientBufferLength + expBufferLength;

private const(C)[] toStringImpl(C = char)(ref scope return C[eDecimalLength] buffer) scope const @safe pure nothrow
///
immutable(C)[] toString(C = char)(NumericSpec spec = NumericSpec.init) const @safe pure nothrow
if(isSomeChar!C && isMutable!C)
{
import mir.appender: UnsafeArrayBuffer;
C[eDecimalLength] data = void;
auto buffer = UnsafeArrayBuffer!C(data);
toString(buffer, spec);
return buffer.data.idup;
}

static if (maxSize64 == 3)
///
version(mir_bignum_test) @safe pure unittest
{
auto str = "-3.4010447314490204552169750449563978034784726557588085989975288830070948234680e-13245";
auto decimal = Decimal!4(str);
assert(decimal.toString == str, decimal.toString);

decimal = Decimal!4.init;
assert(decimal.toString == "0.0");
}

///
void toString(C = char, W)(scope ref W w, NumericSpec spec = NumericSpec.init) const
if(isSomeChar!C && isMutable!C)
{
assert(spec == NumericSpec.exponent || spec == NumericSpec.human);
import mir.utility: _expect;
// handle special values
if (_expect(exponent == exponent.max, false))
{
immutable(C)[] nan = "nan";
immutable(C)[] ninf = "-inf";
immutable(C)[] pinf = "+inf";
return coefficient.length == 0 ? coefficient.sign ? ninf : pinf : nan;
static immutable C[3] nan = "nan";
static immutable C[4] ninf = "-inf";
static immutable C[4] pinf = "+inf";
w.put(coefficient.length == 0 ? coefficient.sign ? ninf[] : pinf[] : nan[]);
return;
}

C[coefficientBufferLength] buffer = void;

size_t coefficientLength;
static if (size_t.sizeof == 8)
{
Expand All @@ -221,87 +251,89 @@ struct Decimal(size_t maxSize64)
}
auto work = BigUIntView!uint(data);
work = work.topLeastSignificantPart(coefficient.length * 2).normalized;
coefficientLength = work.toStringImpl(buffer[0 .. $ - expBufferShift]);
coefficientLength = work.toStringImpl(buffer);
}
else
{
BigInt!maxSize64 work = coefficient;
coefficientLength = work.view.unsigned.toStringImpl(buffer[0 .. $ - expBufferShift]);
coefficientLength = work.view.unsigned.toStringImpl(buffer);
}
}
else
{
BigInt!maxSize64 work = coefficient;
coefficientLength = work.view.unsigned.toStringImpl(buffer[0 .. $ - expBufferShift]);
coefficientLength = work.view.unsigned.toStringImpl(buffer);
}

static immutable C[10] zeros = "-0.00000.0";

if (spec.format == NumericSpec.Format.human)
{
// try print decimal form without exponent
// up to 6 digits exluding leading 0. or final .0
if (this.exponent >= 0)
{
if (this.exponent + coefficientLength <= 6)
{
buffer[$ - coefficientLength - 1] = '-';
w.put(buffer[$ - coefficientLength - coefficient.sign .. $]);
w.put(zeros[$ - (exponent + 2) .. $]);
return;
}
}
else
if (this.exponent < 0)
{
if (this.exponent >= -6 && coefficientLength <= 6)
{
sizediff_t zerosLength = -this.exponent - coefficientLength;
if (zerosLength >= 0)
{
w.put(zeros[!coefficient.sign .. zerosLength + 2 + 1]);
w.put(buffer[$ - coefficientLength .. $]);
return;
}
else
{
buffer[$ - coefficientLength - 1] = '-';
w.put(buffer[$ - coefficientLength - coefficient.sign .. $ - coefficientLength - zerosLength]);
buffer[$ - coefficientLength - zerosLength - 1] = '.';
w.put(buffer[$ - coefficientLength - zerosLength - 1 .. $]);
return;
}
}
}
}

assert(coefficientLength);

sizediff_t exponent = this.exponent + coefficientLength - 1;

if (coefficientLength > 1)
{
auto c = buffer[$ - expBufferShift - coefficientLength];
buffer[$ - expBufferShift - coefficientLength] = '.';
buffer[$ - expBufferShift - ++coefficientLength] = c;
auto c = buffer[$ - coefficientLength];
buffer[$ - coefficientLength] = '.';
buffer[$ - ++coefficientLength] = c;
}

if (coefficient.sign)
{
buffer[$ - expBufferShift - ++coefficientLength] = '-';
buffer[$ - ++coefficientLength] = '-';
}

size_t exponentLength;
{
bool expSign = exponent < 0;
size_t unsignedExponent = expSign ? -exponent : exponent;
size_t i = buffer.length;
w.put(buffer[$ - coefficientLength .. $]);

do
{
buffer[--i] = cast(char)(unsignedExponent % 10 + '0');
unsignedExponent /= 10;
}
while(unsignedExponent);
if (expSign)
buffer[--i] = '-';
exponentLength = buffer.length - i;
}
C[expBufferLength] expBuffer = void;
import mir.format_impl: printSignedToTail;

buffer[$ - expBufferShift] = 'e';

assert(exponentLength <= expBufferShift + 1);
size_t i;
do buffer[$ - (expBufferShift - 1) + i] = buffer[$ - exponentLength + i];
while(++i < exponentLength);
return buffer[$ - (expBufferShift + coefficientLength) .. $ - (expBufferShift - 1) + exponentLength];
}

///
immutable(C)[] toString(C = char)() const @safe pure nothrow
if(isSomeChar!C && isMutable!C)
{
C[eDecimalLength] buffer = void;
return toStringImpl(buffer).idup;
}

static if (maxSize64 == 3)
///
version(mir_bignum_test) @safe pure unittest
{
auto str = "-3.4010447314490204552169750449563978034784726557588085989975288830070948234680e-13245";
auto integer = Decimal!4(str);
assert(integer.toString == str, integer.toString);

integer = Decimal!4.init;
assert(integer.toString == "0e0");
}
static if (sizediff_t.sizeof == 8)
enum N = 21;
else
enum N = 11;

///
void toString(C = char, W)(scope ref W w) const
if(isSomeChar!C && isMutable!C)
{
C[eDecimalLength] buffer = void;
w.put(toStringImpl(buffer));
auto expLength = printSignedToTail(exponent, buffer[$ - N .. $], '\0');
buffer[$ - ++expLength] = 'e';
w.put(buffer[$ - expLength .. $]);
}

static if (maxSize64 == 3)
Expand All @@ -310,9 +342,9 @@ struct Decimal(size_t maxSize64)
{
import mir.format: stringBuf;
auto str = "5.28238923728e-876543210";
auto integer = Decimal!1(str);
auto decimal = Decimal!1(str);
stringBuf buffer;
buffer << integer;
buffer << decimal;
assert(buffer.data == str, buffer.data);
}

Expand Down
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