Parsing Lemon解析器:此规则无法简化
我正试图编写语法来解析模板语言say(或由您选择),但我无法成功解析Parsing Lemon解析器:此规则无法简化,parsing,grammar,lalr,lemon,Parsing,Grammar,Lalr,Lemon,我正试图编写语法来解析模板语言say(或由您选择),但我无法成功解析switch case语句 让我展示一下所需的语法: {% switch username %} {% case "Jim" %} I want to say: {% case "Nik" %} Hello man! {% endcase %} {% case "Bob" %} Hi {% default %} Who ar
switch case
语句
让我展示一下所需的语法:
{% switch username %}
{% case "Jim" %}
I want to say:
{% case "Nik" %}
Hello man!
{% endcase %}
{% case "Bob" %}
Hi
{% default %}
Who are you?
{% endswitch %}
在这里,endcase只是起到了break的作用
我的语法文件的工作部分:
program ::= template_language(Q) . {
status->ret = Q;
}
template_language(R) ::= statement_list(L) . {
R = L;
}
statement_list(R) ::= statement_list(L) statement(S) . {
R = my_list(L, S);
}
statement_list(R) ::= statement(S) . {
R = my_list(NULL, S);
}
statement(R) ::= switch_statement(E) . {
R = E;
}
// empty {% switch expr %} {% endswitch %}
switch_statement(R) ::= OPEN_DELIMITER SWITCH expr(E) CLOSE_DELIMITER OPEN_DELIMITER ENDSWITCH CLOSE_DELIMITER . {
R = my_switch_statement(E, NULL, status->scanner_state);
}
switch_statement(R) ::= OPEN_DELIMITER SWITCH expr(E) CLOSE_DELIMITER case_clauses(C) OPEN_DELIMITER ENDSWITCH CLOSE_DELIMITER . {
R = my_switch_statement(E, C, status->scanner_state);
}
case_clauses(R) ::= case_clauses(C) case_clause(K) . {
R = my_list(C, K);
}
case_clauses(R) ::= case_clause(K) . {
R = my_list(NULL, K);
}
// empty {% case expr %} {% endcase %}
case_clause(R) ::= OPEN_DELIMITER CASE expr(E) CLOSE_DELIMITER OPEN_DELIMITER ENDCASE CLOSE_DELIMITER . {
R = case_clause(E, NULL, status->scanner_state);
}
case_clause(R) ::= OPEN_DELIMITER CASE expr(E) CLOSE_DELIMITER statement_list(T) OPEN_DELIMITER ENDCASE CLOSE_DELIMITER . {
R = case_clause(E, T, status->scanner_state);
}
这只是我语法的一部分,我曾为for
,if
,while
,do
,loop
等工作过语法
但我不知道:
{%case expr%}语句\u列表(T)
不带{%endcase%}
{%default%}语句\u列表(T)
case_clause(R) ::= OPEN_DELIMITER CASE expr(E) CLOSE_DELIMITER statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
1次,但运气不好,明白吗
这条规则不能简化
#2也一样
坦率地说,我理解问题的根源——缺乏案例/违约界限,但实际上我不知道如何解决这个问题
任何帮助都将不胜感激 问题是你的语法是LR(2),而不是LR(1)
许多移位/减少冲突出现,因为直到出现了代码> %{ >之后才知道该怎么做。例如,考虑部分模板(我故意破坏了缩进):
作为旁注,我建议简化语法,不要对空语句列表使用特殊的大小写。只需为
语句列表
使用空的基本大小写即可:
program ::= template_language(Q) . {
status->ret = Q;
}
template_language(R) ::= statement_list(L) . {
R = L;
}
statement_list(R) ::= statement_list(L) statement(S) . {
R = my_list(L, S);
}
statement_list(R) ::= . {
R = NULL;
}
statement(R) ::= switch_statement(E) . {
R = E;
}
switch_statement(R) ::= OPEN_SWITCH expr(E) CLOSE case_clauses(C) OPEN_ENDSWITCH CLOSE . {
R = my_switch_statement(E, C, status->scanner_state);
}
case_clauses(R) ::= case_clauses(C) case_clause(K) . {
R = my_list(C, K);
}
case_clauses(R) ::= . {
R = NULL;
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) OPEN_ENDCASE CLOSE . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_DEFAULT CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
问题是你的语法是LR(2),而不是LR(1)
许多移位/减少冲突出现,因为直到出现了代码> %{ >之后才知道该怎么做。例如,考虑部分模板(我故意破坏了缩进):
作为旁注,我建议简化语法,不要对空语句列表使用特殊的大小写。只需为
语句列表
使用空的基本大小写即可:
program ::= template_language(Q) . {
status->ret = Q;
}
template_language(R) ::= statement_list(L) . {
R = L;
}
statement_list(R) ::= statement_list(L) statement(S) . {
R = my_list(L, S);
}
statement_list(R) ::= . {
R = NULL;
}
statement(R) ::= switch_statement(E) . {
R = E;
}
switch_statement(R) ::= OPEN_SWITCH expr(E) CLOSE case_clauses(C) OPEN_ENDSWITCH CLOSE . {
R = my_switch_statement(E, C, status->scanner_state);
}
case_clauses(R) ::= case_clauses(C) case_clause(K) . {
R = my_list(C, K);
}
case_clauses(R) ::= . {
R = NULL;
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) OPEN_ENDCASE CLOSE . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_DEFAULT CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
{% switch username %} {% case "Jim" %} I want to say: {% case
{% switch username %} {% case "Jim" %} I want to say: {% switch
program ::= template_language(Q) . {
status->ret = Q;
}
template_language(R) ::= statement_list(L) . {
R = L;
}
statement_list(R) ::= statement_list(L) statement(S) . {
R = my_list(L, S);
}
statement_list(R) ::= statement(S) . {
R = my_list(NULL, S);
}
statement(R) ::= switch_statement(E) . {
R = E;
}
// empty {% switch expr %} {% endswitch %}
switch_statement(R) ::= OPEN_SWITCH expr(E) CLOSE OPEN_ENDSWITCH CLOSE . {
R = my_switch_statement(E, NULL, status->scanner_state);
}
switch_statement(R) ::= OPEN_SWITCH expr(E) CLOSE case_clauses(C) OPEN_ENDSWITCH CLOSE . {
R = my_switch_statement(E, C, status->scanner_state);
}
case_clauses(R) ::= case_clauses(C) case_clause(K) . {
R = my_list(C, K);
}
case_clauses(R) ::= case_clause(K) . {
R = my_list(NULL, K);
}
// empty {% case expr %} {% endcase %}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE OPEN_ENDCASE CLOSE . {
R = case_clause(E, NULL, status->scanner_state);
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) OPEN_ENDCASE CLOSE . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_DEFAULT CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
program ::= template_language(Q) . {
status->ret = Q;
}
template_language(R) ::= statement_list(L) . {
R = L;
}
statement_list(R) ::= statement_list(L) statement(S) . {
R = my_list(L, S);
}
statement_list(R) ::= . {
R = NULL;
}
statement(R) ::= switch_statement(E) . {
R = E;
}
switch_statement(R) ::= OPEN_SWITCH expr(E) CLOSE case_clauses(C) OPEN_ENDSWITCH CLOSE . {
R = my_switch_statement(E, C, status->scanner_state);
}
case_clauses(R) ::= case_clauses(C) case_clause(K) . {
R = my_list(C, K);
}
case_clauses(R) ::= . {
R = NULL;
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) OPEN_ENDCASE CLOSE . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_CASE expr(E) CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}
case_clause(R) ::= OPEN_DEFAULT CLOSE statement_list(T) . {
R = case_clause(E, T, status->scanner_state);
}