LALR(1) implementation is not LALR(1) #403
Description
jison --version
0.4.18
Not sure what is implemented, but it isn't LALR(1):
%lex
%%
"b" return 'B'
"e" return 'E'
<<EOF>> return 'EOF';
/lex
%start top
%%
top
: a EOF
;
a
: b
| e
;
b
: c B
;
c
: e
;
e
: E
;
This grammar is SLR(1) and therefore LALR(1). Predictably no conflicts arise with:
jison -p slr test.jison
But:
jison -p lalr test.jison
[....]
States with conflicts:
State 4
a -> e . #lookaheads= EOF B
c -> e . #lookaheads= EOF B
This may be the same bug as #342 from 2017, where it was reported: "Provisionally fixed in the https://github.com/GerHobbelt/jison fork" but this version (installed using npm install jison-gho -g) has the same problem:
jison --version
0.6.1-215
jison -p lalr test.jison
States with conflicts:
State 4 (B @ c -> e .)
a -> e . #lookaheads= [EOF] [B]
c -> e . #lookaheads= [EOF] [B]
However the online demo at:
https://gerhobbelt.github.io/jison/try/
does not have this problem and neither SLR(1) nor LALR(1) flag up any conflicts. Only LR(0) flags up a conflict, as expected as the grammar is not LR(0).
Is there any way to install a fixed version (the one from the online demo)?