19 November 2003

Delimited lists like (a; b; c) often appear in programs, for example when specifing parameters of a function. In order to indentify errors is such lists you can use the LR grammar (eg. bison/flex):
Identifier_List :
   TKLP TKRP { cout << "(empty list)" << endl; } 
 | TKLP Sep_Simple_List Item TKRP { cout << "(last list item)" << endl; } 
 | TKLP Sep_Simple_List error TKRP { cout << "(ERROR in last item)" << endl; } 

Sep_Simple_List :
   Sep_Simple_List Item Sep { cout << "(non-last list item)"; }
 | Sep_Simple_List error Sep { cout << "(ERROR in non-last item)"; }
 | { cout << "(empty sep_list)"; }

To obtain a LL grammar (eg. ANTLR) you need to do some transformations since left-recursive rules like (a::=a b | b) are not allowed.

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