On 23 Jun 2009, at 20:29, Michiel Helvensteijn wrote:
The operator precedences in my language are
static. I just need a way to isolate the different groupings of
precedence
declarations, so that no shift/reduce conflict is resolved by two
declarations from different groupings.
My method can be worked by hand. This is in fact the safe part; I also
made a part where LR is directly modified, and I need to check Knuth's
paper on it - on the todo list :-).
Take this example:
%nonassoc IF_THEN_RULE
%nonassoc "else"
%left '+' '-'
%left '*'
It generates the following relative orders:
IF_THEN_RULE < "else"
IF_THEN_RULE < '+'
IF_THEN_RULE < '-'
IF_THEN_RULE < '*'
"else" < '+'
"else" < '-'
"else" < '*'
'+' < '*'
'- < '*'
But I would prefer if only the following relations were understood:
IF_THEN_RULE < "else"
'+' < '*'
'- < '*'
All the others were unintentional, and might silently (and badly)
resolve a
shift/reduce conflict that I introduced by accident.
What about adding a '%nonassoc "then"', which resolve the dangling
else. The other things should follow.
If that does not help, I can send you my paper (and also if you just
want it :-)).
Hans
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