我是这方面的新手，我正在努力了解这里发生了什么，在那里我得到了两班倒减少冲突。我有语法(如果我遗漏了什么，我可以添加所需的规则(：
%start translation_unit
%token EOF 0 "end of file"
%token LBRA "["
%token RBRA "]"
%token LPAR "("
%token RPAR ")"
%token DOT "."
%token ARROW "->"
%token INCDEC "++ or --"
%token COMMA ","
%token AMP "&"
%token STAR "*"
%token ADDOP "+ or -"
%token EMPH "!"
%token DIVOP "/ or %"
%token CMPO "<, >, <=, or >="
%token CMPE "== or !="
%token DAMP "&&"
%token DVERT "||"
%token ASGN "="
%token CASS "*=, /=, %=, +=, or -="
%token SEMIC ";"
%token LCUR "{"
%token RCUR "}"
%token COLON ":"
%token TYPEDEF "typedef"
%token VOID "void"
%token ETYPE "_Bool, char, or int"
%token STRUCT "struct"
%token ENUM "enum"
%token CONST "const"
%token IF "if"
%token ELSE "else"
%token DO "do"
%token WHILE "while"
%token FOR "for"
%token GOTO "goto"
%token CONTINUE "continue"
%token BREAK "break"
%token RETURN "return"
%token SIZEOF "sizeof"
%token<string> IDF "identifier"
%token<string> TYPEIDF "type identifier"
%token<int> INTLIT "integer literal"
%token<string> STRLIT "string literal"
/////////////////////////////////
%%
/////////////////////////////////
primary_expression:
IDF
| INTLIT
| STRLIT
| LPAR expression RPAR
;
postfix_expression:
primary_expression
| postfix_expression LBRA expression RBRA
| postfix_expression LPAR argument_expression_list_opt RPAR
| postfix_expression DOT IDF
| postfix_expression ARROW IDF
| postfix_expression INCDEC
;
argument_expression_list_opt:
%empty
| argument_expression_list
;
argument_expression_list:
assignment_expression
| argument_expression_list COMMA assignment_expression
;
unary_expression:
postfix_expression
| INCDEC unary_expression
| unary_operator cast_expression
| SIZEOF LPAR type_name RPAR
;
unary_operator:
AMP
| STAR
| ADDOP
| EMPH
;
cast_expression:
unary_expression
;
multiplicative_expression:
cast_expression
| multiplicative_expression STAR cast_expression
| multiplicative_expression DIVOP cast_expression
;
additive_expression:
multiplicative_expression
| additive_expression ADDOP multiplicative_expression
;
relational_expression:
additive_expression
| relational_expression CMPO additive_expression
;
equality_expression:
relational_expression
| equality_expression CMPE relational_expression
;
logical_AND_expression:
equality_expression
| logical_AND_expression DAMP equality_expression
;
logical_OR_expression:
logical_AND_expression
| logical_OR_expression DVERT logical_AND_expression
;
assignment_expression:
logical_OR_expression
| unary_expression assignment_operator assignment_expression
;
assignment_operator:
ASGN
| CASS
;
expression:
assignment_expression
;
constant_expression:
logical_OR_expression
;
declaration:
no_leading_attribute_declaration
;
no_leading_attribute_declaration:
declaration_specifiers init_declarator_list_opt SEMIC
;
init_declarator_list_opt:
%empty
| init_declarator_list
;
declaration_specifiers:
declaration_specifier
| declaration_specifier declaration_specifiers
;
declaration_specifier:
storage_class_specifier
| type_specifier_qualifier
;
init_declarator_list:
init_declarator
| init_declarator_list COMMA init_declarator
;
init_declarator:
declarator
;
storage_class_specifier:
TYPEDEF
;
type_specifier:
VOID
| ETYPE
| struct_or_union_specifier
| enum_specifier
| typedef_name
;
struct_or_union_specifier:
struct_or_union IDF LCUR member_declaration_list RCUR
| struct_or_union IDF
;
struct_or_union:
STRUCT
;
member_declaration_list:
member_declaration
| member_declaration_list member_declaration
;
member_declaration:
specifier_qualifier_list member_declarator_list_opt SEMIC
;
member_declarator_list_opt:
%empty
| member_declarator_list
;
specifier_qualifier_list:
type_specifier_qualifier
| type_specifier_qualifier specifier_qualifier_list
;
type_specifier_qualifier:
type_specifier
| type_qualifier
;
member_declarator_list:
member_declarator
| member_declarator_list COMMA member_declarator
;
member_declarator:
declarator
;
enum_specifier:
ENUM IDF LCUR enumerator_list RCUR
| ENUM IDF LCUR enumerator_list COMMA RCUR
| ENUM IDF
;
enumerator_list:
enumerator
| enumerator_list COMMA enumerator
;
enumerator:
ENUM
| ENUM ASGN constant_expression
;
type_qualifier:
CONST
;
pointer:
STAR type_qualifier_list_opt
| STAR type_qualifier_list_opt pointer
;
pointer_opt:
%empty
| pointer
;
declarator:
pointer_opt direct_declarator
;
direct_declarator:
IDF
| LPAR declarator RPAR
| array_declarator
| function_declarator
;
abstract_declarator:
pointer
| pointer_opt direct_abstract_declarator
;
direct_abstract_declarator:
LPAR abstract_declarator RPAR
| array_abstract_declarator
| function_abstract_declarator
;
direct_abstract_declarator_opt:
%empty
| direct_abstract_declarator
;
array_abstract_declarator:
direct_abstract_declarator_opt LBRA assignment_expression RBRA
;
function_abstract_declarator:
direct_abstract_declarator_opt LPAR parameter_type_list RPAR
;
array_declarator:
direct_declarator LBRA assignment_expression RBRA
;
function_declarator:
direct_declarator LPAR parameter_type_list RPAR
;
type_qualifier_list_opt:
%empty
| type_qualifier_list
;
type_qualifier_list:
type_qualifier
| type_qualifier_list type_qualifier
;
parameter_type_list:
parameter_list
;
parameter_list:
parameter_declaration
| parameter_list COMMA parameter_declaration
;
parameter_declaration:
declaration_specifiers declarator
| declaration_specifiers abstract_declarator_opt
;
abstract_declarator_opt:
%empty
| abstract_declarator
;
type_name:
specifier_qualifier_list abstract_declarator_opt
;
typedef_name:
TYPEIDF
;
statement:
matched
| unmatched
| other
;
other:
expression_statement
| compound_statement
| jump_statement
;
matched:
selection_statement_c
| iteration_statement_c
;
unmatched:
selection_statement_o
| iteration_statement_o
;
compound_statement:
LCUR block_item_list_opt RCUR
;
block_item_list_opt:
%empty
| block_item_list
;
block_item_list:
block_item
| block_item_list block_item
;
block_item:
declaration
| statement
;
expression_statement:
expression_opt SEMIC
;
expression_opt:
%empty
| expression
;
selection_statement_o:
IF LPAR expression RPAR statement
| IF LPAR expression RPAR matched ELSE unmatched
;
selection_statement_c:
IF LPAR expression RPAR matched ELSE matched
;
iteration_statement_o:
WHILE LPAR expression RPAR unmatched
| FOR LPAR expression_opt SEMIC expression_opt SEMIC expression_opt RPAR unmatched
;
iteration_statement_c:
WHILE LPAR expression RPAR matched
| DO statement WHILE LPAR expression RPAR SEMIC
| FOR LPAR expression_opt SEMIC expression_opt SEMIC expression_opt RPAR matched
;
jump_statement:
RETURN expression_opt SEMIC
;
translation_unit:
external_declaration
| translation_unit external_declaration
;
external_declaration:
function_definition
| declaration
;
function_definition:
declaration_specifiers declarator compound_statement
;
/////////////////////////////////
%%
我得到了这种转变/减少冲突：
State 156
85 declarator: pointer_opt . direct_declarator
91 abstract_declarator: pointer_opt . direct_abstract_declarator
"(" shift, and go to state 187
"identifier" shift, and go to state 44
"(" [reduce using rule 111 (direct_abstract_declarator_opt)]
^^conflict with previous "(" ^^
$default reduce using rule 111 (direct_abstract_declarator_opt)
...
State 197
91 abstract_declarator: pointer_opt . direct_abstract_declarator
"(" shift, and go to state 213
"(" [reduce using rule 111 (direct_abstract_declarator_opt)]
^^conflict^^
$default reduce using rule 111 (direct_abstract_declarator_opt)
所以我把这理解为：当我得到"；("我可以做两件事。首先，从direct_declarator中，我得到LPAR所在的LPAR声明器RPAR。"(">
…或…
我可以减少direct_abstract_declarator->array_abstract _declarater->direct_abstact_clarator_opt->direct_abstract-declarator->LPAR所在的LPARabstract_delarator RPAR"(；("又一次。所以我无法决定哪条路是正确的？
我应该如何处理这场冲突？还是我认为这完全错了？
创建偏移减少冲突的最简单方法之一是引入一个表示可选实例的新的非终端：
something_opt
: something
| %empty
有时这会起作用，但更常见的情况是，在某些上下文中，something可能是可选的，也可能不是可选的。换句话说，您有两种不同的产品使用something:
a: something something_else "END_A"
b: something_opt something_else "END_B"
这并不含糊，但它不能用一个令牌前瞻来解析，因为在识别出something之后，解析器必须决定是否将其简化为something_opt，如果下面的文本是b，则这是必要的。CCD_ 6在语义上基本上是无意义的；存在CCD_ 7或者不存在something。如果没有这些细节，解析器就没有问题；它可以继续解析something_else，然后根据它遇到的是END_A还是END_B，它可以决定是减少a还是减少b。
修复方法很简单：不定义something_opt，只需复制生产，这样一个生产有something，另一个没有。
在您的情况下，有问题的可选非终端是direct_abstract_declarator_opt:
direct_abstract_declarator_opt:
%empty
| direct_abstract_declarator
array_abstract_declarator:
direct_abstract_declarator_opt LBRA assignment_expression RBRA
function_abstract_declarator:
direct_abstract_declarator_opt LPAR parameter_type_list RPAR
这些是唯一使用它的地方，所以我们可以通过复制其他两个非终端的产品来消除它：
array_abstract_declarator:
direct_abstract_declarator LBRA assignment_expression RBRA
| LBRA assignment_expression RBRA
function_abstract_declarator:
direct_abstract_declarator LPAR parameter_type_list RPAR
| LPAR parameter_type_list RPAR
如果可能的话，您应该使用这个模型来编写带有可选非终端的语法。它确实需要复制语义操作，但希望语义操作只是对AST节点构建器的简单调用。它会帮你省去很多不必要的悲伤。