CQL2 grammar rules Conflict between "(" booleanExpression ")" and "(" arrayElement ")"

[kunlinyu]

I am develping a c++ parser and evaluator for CQL2 using bison. https://github.com/IndoorSpatial/cql2cpp
When I handling the arrayPredicate, the bison prints some warnings about reduce/reduce conflicts and shift/reduce conflict.
After I go thourgh the whole bison rules file and the BNF file in the standard. I found the reason.

Example 1 consider this query:

A_CONTAINS( (TRUE, FALSE, TRUE), (TRUE, FALSE) )

apperently the evaluation result should be TRUE.

Example 2 But consider about this query:

A_CONTAINS( (TRUE, FALSE, TRUE), ( (TRUE), (FALSE) ) )

The parser will be confused: what is the type of array elements in the second array?
Option 1
according to BNF:

booleanPrimary = function
               | predicate
               | booleanLiteral
               | "(" booleanExpression ")"  // <-----

TRUE -> booleanLiteral -> booleanPrimary -> booleanFactor -> booleanTerm -> booleanExpression
(TRUE) -> ( booleanExpression ) -> booleanPrimary -> booleanFactor -> booleanTerm -> booleanExpression
so the (TRUE) and (FALSE) are boolExpression. basically, Example 2 equals to Example 1 and the evaluation result should be TRUE.

Option 2
according to BNF:

array = "(" ")"  | "(" arrayElement [ { "," arrayElement } ] ")";
arrayElement = characterClause
             | numericLiteral
             | temporalInstance
             | spatialInstance
             | array
             | arithmeticExpression
             | booleanExpression   // <-------
             | propertyName
             | function;

the "(TRUE)" and "(FALSE)" is another array. So the evaluation result should be NULL or error.

I think the reason is, we use "( )" for both booleanExpression and array.
Let's say if we use "( )" for booleanExpression and "[ ]" for array, it is easy to handle it in my parser.
for example of Option1

A_CONTAINS( [TRUE, FALSE, TRUE], [ (TRUE), (FALSE) ] )

for example of Option2

A_CONTAINS( [TRUE, FALSE, TRUE], [ [TRUE], [FALSE] ] )

[pvretano]

@kunlinyu I seem to recall a discussion in the SWG about using "[]" for arrays but I am not sure why we did not do that. Let me go back and check about that. Also, I'll try the grammar with YACC too, just to verify that it complains as well. Please stand by ...