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Editorial: Simplify the |NumericLiteral| grammar #3096

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Editorial: Simplify the |NumericLiteral| grammar #3096

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84335ab
Editorial: Simplify the |DecimalLiteral| grammar
gibson042 Jun 11, 2023
a3ba9a7
Editorial: Simplify the |LegacyOctalIntegerLiteral| grammar
gibson042 Jun 11, 2023
179f705
Editorial: Simplify the bigint literal grammar
gibson042 Jun 11, 2023
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35 changes: 12 additions & 23 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -16548,14 +16548,11 @@ <h2>Syntax</h2>
NumericLiteral ::
DecimalLiteral
DecimalBigIntegerLiteral
NonDecimalIntegerLiteral[+Sep]
NonDecimalIntegerLiteral[+Sep] BigIntLiteralSuffix
NonDecimalIntegerLiteral[+Sep] BigIntLiteralSuffix?
LegacyOctalIntegerLiteral

DecimalBigIntegerLiteral ::
`0` BigIntLiteralSuffix
NonZeroDigit DecimalDigits[+Sep]? BigIntLiteralSuffix
NonZeroDigit NumericLiteralSeparator DecimalDigits[+Sep] BigIntLiteralSuffix
CanonicalDecimalIntegerLiteral BigIntLiteralSuffix

NonDecimalIntegerLiteral[Sep] ::
BinaryIntegerLiteral[?Sep]
Expand All @@ -16573,10 +16570,13 @@ <h2>Syntax</h2>
DecimalFraction[~Empty]

DecimalIntegerLiteral ::
CanonicalDecimalIntegerLiteral
NonOctalDecimalIntegerLiteral

CanonicalDecimalIntegerLiteral ::
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Might there be a better name than CanonicalDecimalIntegerLiteral? It makes me think “canonical numeric string”, which corresponds to neither a superset nor subset of the sequences this production matches.

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Sure, suggestions welcome. But the similarity to "canonical numeric string" is intentional, and the two concepts do mostly agree where they intersect—not for power-of-two numbers large enough that Number::toString uses exponential notation, but I'm willing to chalk that up as a difference between canonicalized numeric strings vs. integer literals (numeric strings and integer literals already being distinct with respect to e.g. supporting _ separators).

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not for power-of-two numbers large enough that Number::toString uses exponential notation

Even without exponential notation, stuff beyond safe integer range won’t always be canonical in the CNS sense, right? For example the source text literal 9007199254740993 evaluates to the Number value whose canonical string representation is 9007199254740992.

the similarity to "canonical numeric string" is intentional

In that case, perhaps I’m alone in thinking the word might be misleading there, so unless others have an opinion it’s probably not worth changing.

`0`
NonZeroDigit
NonZeroDigit NumericLiteralSeparator? DecimalDigits[+Sep]
NonOctalDecimalIntegerLiteral

DecimalFraction[Empty] ::
`.` DecimalDigits[+Sep]
Expand Down Expand Up @@ -16684,10 +16684,10 @@ <h1>Static Semantics: MV</h1>
The MV of <emu-grammar>DecimalBasePart :: DecimalIntegerLiteral DecimalFraction</emu-grammar> is the MV of |DecimalIntegerLiteral| plus the MV of |DecimalFraction|.
</li>
<li>
The MV of <emu-grammar>DecimalIntegerLiteral :: `0`</emu-grammar> is 0.
The MV of <emu-grammar>CanonicalDecimalIntegerLiteral :: `0`</emu-grammar> is 0.
</li>
<li>
The MV of <emu-grammar>DecimalIntegerLiteral :: NonZeroDigit NumericLiteralSeparator? DecimalDigits</emu-grammar> is (the MV of |NonZeroDigit| × 10<sup>_n_</sup>) plus the MV of |DecimalDigits|, where _n_ is the number of code points in |DecimalDigits|, excluding all occurrences of |NumericLiteralSeparator|.
The MV of <emu-grammar>CanonicalDecimalIntegerLiteral :: NonZeroDigit NumericLiteralSeparator? DecimalDigits</emu-grammar> is (the MV of |NonZeroDigit| × 10<sup>_n_</sup>) plus the MV of |DecimalDigits|, where _n_ is the number of code points in |DecimalDigits|, excluding all occurrences of |NumericLiteralSeparator|.
</li>
<li>
The MV of <emu-grammar>DecimalFraction :: `.` DecimalDigits</emu-grammar> is the MV of |DecimalDigits| × 10<sup>-_n_</sup>, where _n_ is the number of code points in |DecimalDigits|, excluding all occurrences of |NumericLiteralSeparator|.
Expand Down Expand Up @@ -16805,22 +16805,10 @@ <h1>Static Semantics: NumericValue ( ): a Number or a BigInt</h1>
<emu-alg>
1. Return the BigInt value that represents the MV of |NonDecimalIntegerLiteral|.
</emu-alg>
<emu-grammar>DecimalBigIntegerLiteral :: `0` BigIntLiteralSuffix</emu-grammar>
<emu-alg>
1. Return *0*<sub>ℤ</sub>.
</emu-alg>
<emu-grammar>DecimalBigIntegerLiteral :: NonZeroDigit BigIntLiteralSuffix</emu-grammar>
<emu-alg>
1. Return the BigInt value that represents the MV of |NonZeroDigit|.
</emu-alg>
<emu-grammar>
DecimalBigIntegerLiteral ::
NonZeroDigit DecimalDigits BigIntLiteralSuffix
NonZeroDigit NumericLiteralSeparator DecimalDigits BigIntLiteralSuffix
</emu-grammar>
<emu-grammar>DecimalBigIntegerLiteral :: CanonicalDecimalIntegerLiteral BigIntLiteralSuffix</emu-grammar>
<emu-alg>
1. Let _n_ be the number of code points in |DecimalDigits|, excluding all occurrences of |NumericLiteralSeparator|.
1. Let _mv_ be (the MV of |NonZeroDigit| × 10<sup>_n_</sup>) plus the MV of |DecimalDigits|.
1. Let _mv_ be the MV of |CanonicalDecimalIntegerLiteral|.
1. Assert: _mv_ is an integer.
1. Return ℤ(_mv_).
</emu-alg>
</emu-clause>
Expand Down Expand Up @@ -47443,6 +47431,7 @@ <h1>Lexical Grammar</h1>
<emu-prodref name="DecimalLiteral"></emu-prodref>
<emu-prodref name="DecimalBasePart"></emu-prodref>
<emu-prodref name="DecimalIntegerLiteral"></emu-prodref>
<emu-prodref name="CanonicalDecimalIntegerLiteral"></emu-prodref>
<emu-prodref name="DecimalFraction"></emu-prodref>
<emu-prodref name="DecimalDigits"></emu-prodref>
<emu-prodref name="DecimalDigit"></emu-prodref>
Expand Down