CODEWITHSUNDEEP
parsingbison
ronny
ronny

Reputation: 3

bison shift/reduce conflict

in the following simple grammar, on the conflict at state 4, can 'shift' become the taken action without changing the rules ? (I thought that by default shift was bison's preferred action)

%token one two three

%%

start : a;
a : X Y Z;
X : one;
Z : two | three;
Y : two | ;

%%

Upvotes: 0

Views: 155

Answers (2)

Chris Dodd
Chris Dodd

Reputation: 126478

Shift is the default, but that results in the generated parser giving an error for the input one two so that is probably not what you want. Instead, follow rici's advice and fix the grammar.

Upvotes: 1

rici
rici

Reputation: 241911

shift is bison's preferred action, and you can see in the state output that it will shift two in state 4. It will still report a shift-reduce conflict, but you can take that as a warning if you like. (See %expect.) You'd probably be better off fixing the grammar:

start : a;
a : X Z | X Y Z;
X : one;
Y : two;
Z : two | three;

Upvotes: 3

Related Questions