转移/减少合流层yacc

Question

我正在执行ply yacc编译器，并收到以下警告：

WARNING: 9 shift/reduce conflicts

下面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（使用MUL_op、ADD_op、COMPARATOR）。但我想不出解决的办法，你知道吗

多谢各位

Answer 1

正如@rici所说，我的代码缺少优先顺序：

以下代码解决了该问题：

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

谢谢大家!