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Prateek R Karandikar
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 Posted: Mon May 24, 2004 7:02 pm Post subject: Whitespace ambiguity in grammar |
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When there are 2 consecutive elements of grammar, sometimes it is
intended that whitespace be required between them, someimes that there
be no whitespace between them, and sometimes that whitespace is
optional.
For ex,
1)
original-namespace-definition:
namespace identifier { namespace-body }
Clearly, whitespace is required between namespace and identifier.
2)
decimal-literal:
nonzero-digit
decimal-literal digit
Clearly, it is required that there be no whitespace between
decimal-literal and digit.
3)
and-expression:
equality-expression
and-expression & equality-expression
Clearly, whitespace is optional on both sides of the &.
Isn't this inconsistent?
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Victor Bazarov
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| Posted: Mon May 24, 2004 8:29 pm Post subject: Re: Whitespace ambiguity in grammar |
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Prateek R Karandikar wrote:
| Quote: | When there are 2 consecutive elements of grammar, sometimes it is
intended that whitespace be required between them, someimes that there
be no whitespace between them, and sometimes that whitespace is
optional.
For ex,
1)
original-namespace-definition:
namespace identifier { namespace-body }
Clearly, whitespace is required between namespace and identifier.
2)
decimal-literal:
nonzero-digit
decimal-literal digit
Clearly, it is required that there be no whitespace between
decimal-literal and digit.
3)
and-expression:
equality-expression
and-expression & equality-expression
Clearly, whitespace is optional on both sides of the &.
Isn't this inconsistent?
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No. I think you need to look at the translation phases (2.1), pay
attention to the definition of "preprocessing token" and "token", and to
the paragraph 2.1/7. The rule concerning the original namespace
definition is given in terms of tokens, and with those whitespace is not
important. It's only important when determining the token sequence.
V
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