diff --git a/spec.html b/spec.html index 55bcc4ae4a5..96acf7b2988 100644 --- a/spec.html +++ b/spec.html @@ -4277,7 +4277,7 @@

ToNumber ( _argument_ )

String - See grammar and conversion algorithm below. + Return ! StringToNumber(_argument_). @@ -4314,7 +4314,7 @@

ToNumber ( _argument_ )

ToNumber Applied to the String Type

-

ToNumber applied to Strings applies the following grammar to the input String interpreted as a sequence of UTF-16 encoded code points (). If the grammar cannot interpret the String as an expansion of |StringNumericLiteral|, then the result of ToNumber is *NaN*.

+

The abstract operation StringToNumber specifies how to convert a String value to a Number value. Overall, the process is similar to the determination of the NumericValue of a numeric literal (see ), but some of the details are different.

Syntax

StringNumericLiteral ::: @@ -4370,7 +4370,6 @@

Syntax

Runtime Semantics: MV

-

The conversion of a String to a Number value is similar overall to the determination of the Number value for a numeric literal (see ), but some of the details are different, so the process for converting a String numeric literal to a value of Number type is given here. This value is determined in two steps: first, a mathematical value (MV) is derived from the String numeric literal; second, this mathematical value is rounded as described below. The MV on any grammar symbol, not provided below, is the MV for that symbol defined in .

  • The MV of StringNumericLiteral ::: [empty] is 0. @@ -4406,7 +4405,29 @@

    Runtime Semantics: MV

    The MV of StrUnsignedDecimalLiteral ::: DecimalDigits ExponentPart is the MV of |DecimalDigits| times 10_e_, where _e_ is the MV of |ExponentPart|.
-

Once the exact MV for a String numeric literal has been determined, it is then rounded to a value of the Number type. If the MV is 0, then the rounded value is *+0*𝔽 unless the first non white space code point in the String numeric literal is `-`, in which case the rounded value is *-0*𝔽. Otherwise, the rounded value must be the Number value for the MV (in the sense defined in ), unless the literal includes a |StrUnsignedDecimalLiteral| and the literal has more than 20 significant digits, in which case the Number value may be either the Number value for the MV of a literal produced by replacing each significant digit after the 20th with a 0 digit or the Number value for the MV of a literal produced by replacing each significant digit after the 20th with a 0 digit and then incrementing the literal at the 20th digit position. A digit is significant if it is not part of an |ExponentPart| and

+

For the MV of any production not shown above, see .

+ + + +

StringToNumber ( _str_ )

+

The abstract operation StringToNumber takes argument _str_ (a String) and returns a Number. It performs the following steps when called:

+ + 1. Let _text_ be ! StringToCodePoints(_str_). + 1. Let _literal_ be ParseText(_text_, |StringNumericLiteral|). + 1. If _literal_ is a List of errors, return *NaN*. + 1. If _literal_ contains a |StrUnsignedDecimalLiteral| and _literal_ has more than 20 significant digits, then + 1. Let _lit_ be an implementation-defined choice of: + * _literal_ + * a literal produced from _literal_ by replacing each significant digit after the 20th with a `0` digit + * a literal produced from _literal_ by replacing each significant digit after the 20th with a `0` digit and then incrementing the literal at the 20th significant digit position + 1. Else, + 1. Let _lit_ be _literal_. + 1. Let _mv_ be the MV of _lit_. + 1. If _mv_ is 0 and the first non white space code point in _text_ is `-`, return *-0*𝔽. + 1. Return 𝔽(_mv_). + + +

A digit is significant if it is not part of an |ExponentPart| and

  • it is not `0`; or @@ -11027,7 +11048,7 @@

    Syntax

    Static Semantics: MV

    -

    A numeric literal stands for a value of the Number type or the BigInt type.

    +

    A numeric literal stands for a value of the Number type or the BigInt type, as specified by the syntax-directed operation NumericValue. Determining this value involves deriving a mathematical value (MV) from the literal, according to the following rules.

    • The MV of NumericLiteral :: DecimalLiteral is the MV of |DecimalLiteral|. @@ -11193,15 +11214,26 @@

      Static Semantics: MV

      Static Semantics: NumericValue

      - NumericLiteral :: DecimalLiteral + NumericLiteral :: NonDecimalIntegerLiteral - 1. Return the Number value that results from rounding the MV of |DecimalLiteral| as described below. + 1. Let _mv_ be the MV of |NonDecimalIntegerLiteral|. + 1. Return 𝔽(_mv_). - NumericLiteral :: NonDecimalIntegerLiteral + + NumericLiteral :: DecimalLiteral - 1. Return the Number value that results from rounding the MV of |NonDecimalIntegerLiteral| as described below. + 1. If |DecimalLiteral| has more than 20 significant digits, then + 1. Let _lit_ be an implementation-defined choice of: + * |DecimalLiteral| + * a literal produced from |DecimalLiteral| by replacing each significant digit after the 20th with a `0` digit + * a literal produced from |DecimalLiteral| by replacing each significant digit after the 20th with a `0` digit and then incrementing the literal at the 20th significant digit position + 1. Else, + 1. Let _lit_ be |DecimalLiteral|. + 1. Let _mv_ be the MV of _lit_. + 1. Return 𝔽(_mv_). -

      Once the exact MV for a numeric literal has been determined, it is then rounded to a value of the Number type. If the MV is 0, then the rounded value is *+0*𝔽; otherwise, the rounded value must be the Number value for the MV (as specified in ), unless the literal is a |DecimalLiteral| and the literal has more than 20 significant digits, in which case the Number value may be either the Number value for the MV of a literal produced by replacing each significant digit after the 20th with a `0` digit or the Number value for the MV of a literal produced by replacing each significant digit after the 20th with a `0` digit and then incrementing the literal at the 20th significant digit position. A digit is significant if it is not part of an |ExponentPart| and

      + +

      A digit is significant if it is not part of an |ExponentPart| and

      • it is not `0`; or