RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-25 17:47:44 +00:00
Code Issues Activity Actions

LibJS: Define number_to_string to convert a double to a String

Browse source
This commit is contained in:
Timothy Flynn 2023-01-13 12:22:20 -05:00 • committed by Linus Groh
parent 8a88d4434f
commit 0b58748156
2 changed files with 54 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

85
Userland/Libraries/LibJS/Runtime/Value.cpp
View file

@ -72,7 +72,7 @@ ALWAYS_INLINE bool both_bigint(Value const& lhs, Value const& rhs)
// 6.1.6.1.20 Number::toString ( x ), https://tc39.es/ecma262/#sec-numeric-types-number-tostring
// Implementation for radix = 10
DeprecatedString number_to_deprecated_string(double d, NumberToStringMode mode)
static ErrorOr<void> number_to_string_impl(StringBuilder& builder, double d, NumberToStringMode mode)
{
auto convert_to_decimal_digits_array = [](auto x, auto& digits, auto& length) {
for (; x; x /= 10)
@ -82,22 +82,27 @@ DeprecatedString number_to_deprecated_string(double d, NumberToStringMode mode)
};
// 1. If x is NaN, return "NaN".
if (isnan(d))
return "NaN";
if (isnan(d)) {
TRY(builder.try_append("NaN"sv));
return {};
}
// 2. If x is +0𝔽 or -0𝔽, return "0".
if (d == +0.0 || d == -0.0)
return "0";
if (d == +0.0 || d == -0.0) {
TRY(builder.try_append("0"sv));
return {};
}
// 4. If x is +∞𝔽, return "Infinity".
if (isinf(d)) {
if (d > 0)
return "Infinity";
else
return "-Infinity";
}
if (d > 0) {
TRY(builder.try_append("Infinity"sv));
return {};
}
StringBuilder builder;
TRY(builder.try_append("-Infinity"sv));
return {};
}
// 5. Let n, k, and s be integers such that k ≥ 1, radix ^ (k - 1) ≤ s < radix ^ k,
// 𝔽(s × radix ^ (n - k)) is x, and k is as small as possible. Note that k is the number of
@ -115,7 +120,7 @@ DeprecatedString number_to_deprecated_string(double d, NumberToStringMode mode)
// 3. If x < -0𝔽, return the string-concatenation of "-" and Number::toString(-x, radix).
if (sign)
builder.append('-');
TRY(builder.try_append('-'));
// Non-standard: Intl needs number-to-string conversions for extremely large numbers without any
// exponential formatting, as it will handle such formatting itself in a locale-aware way.
@ -127,34 +132,34 @@ DeprecatedString number_to_deprecated_string(double d, NumberToStringMode mode)
if (n >= k) {
// i. Return the string-concatenation of:
// the code units of the k digits of the representation of s using radix radix
builder.append(mantissa_digits.data(), k);
TRY(builder.try_append(mantissa_digits.data(), k));
// n - k occurrences of the code unit 0x0030 (DIGIT ZERO)
builder.append_repeated('0', n - k);
TRY(builder.try_append_repeated('0', n - k));
// b. Else if n > 0, then
} else if (n > 0) {
// i. Return the string-concatenation of:
// the code units of the most significant n digits of the representation of s using radix radix
builder.append(mantissa_digits.data(), n);
TRY(builder.try_append(mantissa_digits.data(), n));
// the code unit 0x002E (FULL STOP)
builder.append('.');
TRY(builder.try_append('.'));
// the code units of the remaining k - n digits of the representation of s using radix radix
builder.append(mantissa_digits.data() + n, k - n);
TRY(builder.try_append(mantissa_digits.data() + n, k - n));
// c. Else,
} else {
// i. Assert: n ≤ 0.
VERIFY(n <= 0);
// ii. Return the string-concatenation of:
// the code unit 0x0030 (DIGIT ZERO)
builder.append('0');
TRY(builder.try_append('0'));
// the code unit 0x002E (FULL STOP)
builder.append('.');
TRY(builder.try_append('.'));
// -n occurrences of the code unit 0x0030 (DIGIT ZERO)
builder.append_repeated('0', -n);
TRY(builder.try_append_repeated('0', -n));
// the code units of the k digits of the representation of s using radix radix
builder.append(mantissa_digits.data(), k);
TRY(builder.try_append(mantissa_digits.data(), k));
}
return builder.to_deprecated_string();
return {};
}
// 7. NOTE: In this case, the input will be represented using scientific E notation, such as 1.2e+3.
@ -173,31 +178,45 @@ DeprecatedString number_to_deprecated_string(double d, NumberToStringMode mode)
if (k == 1) {
// a. Return the string-concatenation of:
// the code unit of the single digit of s
builder.append(mantissa_digits[0]);
TRY(builder.try_append(mantissa_digits[0]));
// the code unit 0x0065 (LATIN SMALL LETTER E)
builder.append('e');
TRY(builder.try_append('e'));
// exponentSign
builder.append(exponent_sign);
TRY(builder.try_append(exponent_sign));
// the code units of the decimal representation of abs(n - 1)
builder.append(exponent_digits.data(), exponent_length);
TRY(builder.try_append(exponent_digits.data(), exponent_length));
return builder.to_deprecated_string();
return {};
}
// 12. Return the string-concatenation of:
// the code unit of the most significant digit of the decimal representation of s
builder.append(mantissa_digits[0]);
TRY(builder.try_append(mantissa_digits[0]));
// the code unit 0x002E (FULL STOP)
builder.append('.');
TRY(builder.try_append('.'));
// the code units of the remaining k - 1 digits of the decimal representation of s
builder.append(mantissa_digits.data() + 1, k - 1);
TRY(builder.try_append(mantissa_digits.data() + 1, k - 1));
// the code unit 0x0065 (LATIN SMALL LETTER E)
builder.append('e');
TRY(builder.try_append('e'));
// exponentSign
builder.append(exponent_sign);
TRY(builder.try_append(exponent_sign));
// the code units of the decimal representation of abs(n - 1)
builder.append(exponent_digits.data(), exponent_length);
TRY(builder.try_append(exponent_digits.data(), exponent_length));
return {};
}
ThrowCompletionOr<String> number_to_string(VM& vm, double d, NumberToStringMode mode)
{
StringBuilder builder;
TRY_OR_THROW_OOM(vm, number_to_string_impl(builder, d, mode));
return TRY_OR_THROW_OOM(vm, builder.to_string());
}
DeprecatedString number_to_deprecated_string(double d, NumberToStringMode mode)
{
StringBuilder builder;
MUST(number_to_string_impl(builder, d, mode));
return builder.to_deprecated_string();
}