On 02/06/2012 06:49 PM, Mark S. Miller wrote:
On Mon, Feb 6, 2012 at 3:26 PM, Waldemar Horwat <walde...@google.com
<mailto:walde...@google.com>> wrote:
On 02/03/2012 08:07 PM, Mark S. Miller wrote:
On Fri, Feb 3, 2012 at 12:58 PM, Waldemar Horwat <walde...@google.com
<mailto:walde...@google.com> <mailto:walde...@google.com
<mailto:walde...@google.com>>> wrote:
On 02/02/2012 06:27 PM, Waldemar Horwat wrote:
[...]
Note that this is more complex than just having the parser switch
modes for the treatment of / as division vs. regexp. Here comments and white
space are also affected, which can in turn the structure of the lexer upside
down. The kinds of cases I'm thinking of are:
`abc$/*comment*/identifier//
`
(here we have a /**/ comment and a // comment)
There is no valid quasiHole above, so the whole thing matches a
QuasiOnly. The QuasiOnly includes all characters between the backticks. Nothing
is taken to be a comment, just like it wouldn't be if it appeared within a
string.
According to which lexical grammar? According to the one you provided
earlier in this thread, `abc$ is a QuasiOpen token:
QuasiOpen ::
` QuasiChar* $
Parsing further, /*comment*/identifier is a single identifier token as far
as the syntactic grammar is concerned.
I was imprecise. I'll try again, using only lexical grammar concepts and making
explicit where whitespace, comments, etc may appear.
Token ::
IdentifierName
Punctuator
NumericLiteral
StringLiteral
Quasi
Quasi ::
QuasiOnly
QuasiOpen QuasiHole (QuasiMiddle QuasiHole)* QuasiClose
QuasiOnly ::
` QuasiChar* `
QuasiOpen ::
` QuasiChar* $
QuasiMiddle ::
QuasiChar* $
QuasiEnd ::
QuasiChar* `
QuasiChar ::
SourceCharacter *but not one of $ or `*
$ $
$ `
$ \ EscapeSequence
QuasiHole ::
Identifier
{ Spacing* (BalancedCurlySequence Spacing*)* }
BalancedCurlySequence ::
Token *but not one of { or }*
{ Spacing* (BalancedCurlySequence Spacing*)* }
Spacing ::
WhiteSpace
LineTerminator
Comment
Within a Quasi, no character sequences are interpreted as whitespace or
comments except where indicated by Spacing above.
That's going back to the previous approach of treating the whole quasi as a
single token. This doesn't work because it's not possible to specify the
BalancedCurlySequence production as a lexical grammar. You're confusing the
lexical with the syntactic grammars here.
Examples of why BalancedCurlySequence doesn't work:
{/[{]/}
(interior parses as five single-character tokens but no matching closing
bracket)
{ainb}
(interior parses as three tokens: a in b)
{3.toString()}
(interior parses as 3 . toString ( ))
Waldemar
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