add percentage parsing

Author: 9il

source/mir/bignum/decimal.d

@@ -46,11 +46,11 @@ struct Decimal(size_t maxSize64)
  }
 
  ///
- this(C)(scope const(C)[] str) @safe pure @nogc
+ this(C)(scope const(C)[] str, int exponentShift = 0) @safe pure @nogc
  if (isSomeChar!C)
  {
  DecimalExponentKey key;
- if (fromStringImpl(str, key) || key == DecimalExponentKey.nan || key == DecimalExponentKey.infinity)
+ if (fromStringImpl(str, key, exponentShift) || key == DecimalExponentKey.nan || key == DecimalExponentKey.infinity)
  return;
  static if (__traits(compiles, () @nogc { throw new Exception("Can't parse Decimal."); }))
  {
@@ -119,7 +119,16 @@ struct Decimal(size_t maxSize64)
  Returns: false in case of overflow or incorrect string.
  Precondition: non-empty coefficients.
  +/
- bool fromStringImpl(C, bool allowSpecialValues = true, bool allowDotOnBounds = true, bool allowDExponent = true, bool allowStartingPlus = true, bool checkEmpty = true, bool allowUnderscores = true, bool allowLeadingZeros = true)(scope const(C)[] str, out DecimalExponentKey key)
+ bool fromStringImpl(C,
+ bool allowSpecialValues = true,
+ bool allowDotOnBounds = true,
+ bool allowDExponent = true,
+ bool allowStartingPlus = true,
+ bool allowUnderscores = true,
+ bool allowLeadingZeros = true,
+ bool checkEmpty = true,
+ )
+ (scope const(C)[] str, out DecimalExponentKey key, int exponentShift = 0)
  @safe pure @nogc nothrow
  if (isSomeChar!C)
  {
@@ -161,7 +170,6 @@ struct Decimal(size_t maxSize64)
  exponent = 0;
 
  ulong v;
- uint afterDot;
  bool dot;
  static if (allowUnderscores)
  {
@@ -225,11 +233,11 @@ struct Decimal(size_t maxSize64)
  }
  S:
  v += d;
- afterDot += dot;
+ exponentShift -= dot;
  if (str.length)
  continue;
  E:
- exponent -= afterDot;
+ exponent += exponentShift;
  R:
  coefficient.data[0] = v;
  coefficient.length = v != 0;
@@ -321,7 +329,7 @@ struct Decimal(size_t maxSize64)
  {
  import mir.bignum.low_level_view: DecimalView, BigUIntView, MaxWordPow10;
  auto work = DecimalView!size_t(false, 0, BigUIntView!size_t(coefficient.data));
- auto ret = work.fromStringImpl!(C, allowSpecialValues, allowDExponent, allowStartingPlus, checkEmpty, allowUnderscores, allowLeadingZeros)(str, key);
+ auto ret = work.fromStringImpl!(C, allowSpecialValues, allowDExponent, allowStartingPlus, allowUnderscores, allowLeadingZeros, checkEmpty)(str, key, exponentShift);
  coefficient.length = cast(uint) work.coefficient.coefficients.length;
  coefficient.sign = work.sign;
  exponent = work.exponent;
@@ -339,9 +347,11 @@ struct Decimal(size_t maxSize64)
  Decimal!3 decimal;
  DecimalExponentKey key;
 
- assert(decimal.fromStringImpl("1.334", key));
+ // Check precise percentate parsing
+ assert(decimal.fromStringImpl("71.7", key, -2));
  assert(key == DecimalExponentKey.dot);
- assert(cast(double) decimal == 1.334);
+ // The result is exact value instead of 0.7170000000000001 = 71.7 / 100
+ assert(cast(double) decimal == 0.717);
 
  assert(decimal.fromStringImpl("+0.334e-5"w, key));
  assert(key == DecimalExponentKey.e);

source/mir/bignum/low_level_view.d

@@ -2046,9 +2046,17 @@ struct DecimalView(W, WordEndian endian = TargetEndian, Exp = sizediff_t)
  /++
  Returns: false in case of overflow or incorrect string.
  Precondition: non-empty coefficients
- Note: doesn't support signs.
  +/
- bool fromStringImpl(C, bool allowSpecialValues = true, bool allowDotOnBounds = true, bool allowDExponent = true, bool allowStartingPlus = true, bool checkEmpty = true, bool allowUnderscores = true, bool allowLeadingZeros = true)(scope const(C)[] str, out DecimalExponentKey key)
+ bool fromStringImpl(C,
+ bool allowSpecialValues = true,
+ bool allowDotOnBounds = true,
+ bool allowDExponent = true,
+ bool allowStartingPlus = true,
+ bool allowUnderscores = true,
+ bool allowLeadingZeros = true,
+ bool checkEmpty = true,
+ )
+ (scope const(C)[] str, out DecimalExponentKey key, int exponentShift = 0)
  @safe pure @nogc nothrow
  if (isSomeChar!C)
  {
@@ -2094,7 +2102,6 @@ struct DecimalView(W, WordEndian endian = TargetEndian, Exp = sizediff_t)
 
  W v;
  W t = 1;
- uint afterDot;
  bool dot;
 
  static if (allowUnderscores)
@@ -2159,7 +2166,7 @@ struct DecimalView(W, WordEndian endian = TargetEndian, Exp = sizediff_t)
  S:
  t *= 10;
  v += d;
- afterDot += dot;
+ exponentShift -= dot;
 
  if (_expect(t == mp10 || str.length == 0, false))
  {
@@ -2182,7 +2189,7 @@ struct DecimalView(W, WordEndian endian = TargetEndian, Exp = sizediff_t)
  if (str.length == 0)
  {
  M:
- exponent -= afterDot;
+ exponent += exponentShift;
  coefficient = work.mostSignificant == 0 ? coefficient.init : work;
  static if (allowUnderscores)
  {