Hello
I have a grammar to do for my self, and since this grammar add the
same expression than the one we could have in a SQL query language,
I'm wondering which grammar is better in term of performance.
My first one is the classical "one production per precedence" :
start: VARSTART e_no_prec VAREND
;
e_no_prec: e_xor OR e_no_prec
| e_xor
;
e_xor: e_and XOR e_xor
| e_and
;
e_and: e_equal_in AND e_and
| e_equal_in
;
e_equal_in: e_cmp IN e_cmp
| e_cmp IS e_cmp
| e_cmp EQ e_cmp
| e_cmp NE e_cmp
| e_cmp '=' e_cmp
| e_cmp
;
e_cmp: e_additive '<' e_additive
| e_additive '>' e_additive
| e_additive LE e_additive
| e_additive GE e_additive
| e_additive BETWEEN e_additive AND e_additive
| e_additive
;
e_additive: e_mult '+' e_additive
| e_mult '-' e_additive
| e_mult CONCAT e_additive
| e_mult
;
e_mult: e_final '/' e_mult
| e_final '*' e_mult
| e_final '%' e_mult
| e_final
;
e_final: '(' e_no_prec ')'
| constant
| variable
;
This works fine, and do what I want. But I've got a lot of rules, and
it give me 70 states for the automata.
With %left, and %nonassoc (and %right too) it give this :
start: VARSTART expr VAREND
;
expr: expr XTF_T_LOGICAL_OR expr
| expr XTF_T_LOGICAL_XOR expr
| expr XTF_T_LOGICAL_AND expr
| expr_no_and
;
expr_no_and: expr_no_and XTF_T_IN expr_no_and
| expr_no_and XTF_T_IS expr_no_and
| expr_no_and XTF_T_CMP_EQ expr_no_and
| expr_no_and '=' expr_no_and
| expr_no_and XTF_T_CMP_NE expr_no_and
| expr_no_and '<' expr_no_and
| expr_no_and '>' expr_no_and
| expr_no_and XTF_T_CMP_GE expr_no_and
| expr_no_and XTF_T_CMP_LE expr_no_and
| expr_no_and XTF_T_BETWEEN expr_no_and XTF_T_LOGICAL_AND expr_no_and
| expr_no_and '+' expr_no_and
| expr_no_and '-' expr_no_and
| expr_no_and XTF_T_STRING_CONCAT expr_no_and
| expr_no_and '/' expr_no_and
| expr_no_and '%' expr_no_and
| expr_no_and '*' expr_no_and
| '(' expr ')'
| constant
| variable
;
(constant and variable are the same in the two grammars).
This also works fine, and give me 64 states : but the Output file
shows me a bigger automata in term of transition.
The second one is based on the grammar provided by PHP, and mySQL
(respectivly zend_language_parser.y and sql_parser.yy).
The problem here is that I actually don't know which one I should
choose : the first get more state, but less transition per state, so
it not so bad. The second give less state, but more transition per
states.
Finally, I want to translate the generated parser in PHP, for that I
have to parse the output file to get some arrays and by the time,
create some kind of transition table (well, it was my first idea) :
Is there a better method ? (I don't understand how work exactly the
algorithm in Bison, and I don't know if I can handle it without using
goto like Bison does).
Notice that I don't want to write a manual parser (aka: using one
function per rules) since it must be written in PHP, and I prefer
avoiding them.
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