Hello,
sorry for an off-topic thing. But I guess somebody here could help me...
I have a problem with bison grammer
Having
%token ATOM
%left '+'
%left REP
and a grammar:
block: ATOM
| REP block
| block '+' block
;
is ok. Having another grammer:
block: ATOM
| REP block
| block block %prec '+'
;
has 2 shift/reduce conflicts, similar to
state 7
5 block: REP block .
6 | block . block
ATOM shift, and go to state 3
ATOM [reduce using rule 5 (block)]
$default reduce using rule 5 (block)
block go to state 9
or
state 9
6 block: block . block
6 | block block .
ATOM shift, and go to state 3
REP shift, and go to state 4
ATOM [reduce using rule 6 (block)]
$default reduce using rule 6 (block)
block go to state 9
What I want is to have a parser that can read e.g. (the spaces are
left out by lex, they are not in what bison sees; I only write them
here for better readability)
12 Au 13 Cu 2 Ag
the former grammer (REP is for repetition) is able to read
12 Au + 13 Cu + 2 Ag
but I don't like those pluses, which are redundant.
Also important: I have those 'block' non-terminals there, since I want
to add another rule
block: '[' block ']'
so that I can use brackets and can parse things like
12 [ 2 Cu 3 Co]
Could anyone explain to me what goes wrong?
I can't figure it out...
Thanks a lot
Ruda
PS.: the grammer is actually identical to a grammer that can evaluate
expressions with +, *, and brackets, with usual operator precedence.
