19.1.5

Problem #5: Cast versus Parenthesized Expression

LALR(1) GRAMMAR

class Problem4 { Problem4() { peter[

When the parser is considering the token

peter

, with one token lookahead to

symbol

[

, it cannot yet tell whether

peter

 will be part of a type name, as in:

peter[] team;

or part of an array access, as in:

peter[3] = 12;

Therefore, after the parser reduces

peter

 to the nonterminal

Name

, it cannot tell

with only one token lookahead whether

Name

 should be reduced ultimately to

Type

 (for an array type) or left alone (for an array access). Therefore, the produc 

tions shown above result in a grammar that is not LALR(1).

The solution is to have separate alternatives for

ArrayType

:

ArrayType:

PrimitiveType

 [ ]

Name

 [ ]

ArrayType

 [ ]

This allows the parser to reduce

peter

 to

Name

 and then leave it as is, delaying

the decision as to whether an array type or array access is in progress.

19.1.5   Problem #5: Cast versus Parenthesized Expression

Consider the production:

CastExpression:

(

PrimitiveType

 )

UnaryExpression

(

ReferenceType

 )

UnaryExpressionNotPlusMinus

Now consider the partial input:

class Problem5 { Problem5() { super((matthew)

When the parser is considering the token

matthew

, with one token lookahead to

symbol

)

, it cannot yet tell whether

(matthew)

 will be a parenthesized expres 

sion, as in:

super((matthew), 9);

or a cast, as in:

super((matthew)baz, 9);

Therefore, after the parser reduces

matthew

 to the nonterminal

Name

, it cannot

tell with only one token lookahead whether

Name

 should be further reduced to

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