Shift/reduce 冲突层 yacc

Question

我正在做一个 ply yacc 编译器，我有以下警告：

WARNING: 9 shift/reduce conflicts

这是我创建语法树的规则。

def p_programme_statement(p):
''' programme : statement  '''
p[0] = AST.ProgramNode(p[1])

def p_programme_recursive(p):
    ''' programme : statement ENTER programme '''
    p[0] = AST.ProgramNode([p[1]]+p[3].children)

def p_statement(p):
    ''' statement : assignation
            | structure  '''
    p[0] = p[1]

def p_expression_num_or_var(p):
    '''expression : INT
        | FLOAT 
        | IDENTIFIER 
        '''
    p[0] = AST.TokenNode(p[1])

def p_expression_op(p):
    ''' expression : expression MUL_OP expression 
    | expression ADD_OP expression
    | expression COMPARATOR expression '''
    p[0] = AST.OpNode(p[2], [p[1], p[3]])

def p_assign(p):
    ''' assignation : IDENTIFIER EQU expression '''
    p[0] = AST.AssignNode([AST.TokenNode(p[1]),p[3]])


def p_statement_print(p):
    ''' statement : PRINT expression '''
    p[0] = AST.PrintNode(p[2])


def p_structure_if(p):
    '''structure : IF expression POINTS ENTER TAB programme '#' '''
    p[0] = AST.IfNode([p[2],p[6]])

def p_structure_function(p):
    '''structure : DEF expression '(' ')' POINTS ENTER TAB programme '#' '''
    p[0] = AST.FunctionNode([p[2],p[8]])

def p_structure_while(p):
    ''' structure : WHILE expression POINTS ENTER TAB programme '#' '''
    p[0] = AST.WhileNode([p[2],p[6]])

def p_expression_paren(p):
    '''expression : '(' expression ')' '''
    p[0] = p[2]

冲突发生在 p_expression_op 函数上（与 MUL_OP、ADD_OP、COMPARATOR）。但是我想不出解决办法，你有什么想法吗？

谢谢

Answer 1

正如@rici 所说，我的代码中缺少优先顺序：

以下代码解决了问题：

precedence = (
('left', 'ADD_OP'),
('left', 'MUL_OP'),
('left','COMPARATOR')
)

谢谢！

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