19.1.4 Problem #4: Array Type versus Array Access

Consider the productions (shown after problem #1 has been corrected):

ArrayType:

	Type [ ]

and:

ArrayAccess:

	Name [ Expression ]

	PrimaryNoNewArray [ Expression ]

Now consider the partial input:

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 productions 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.