parser.py 文件源码

def p_additiveExpr_impl(self, p):
        '''additiveExpr : additiveExpr '+' multiplicitiveExpr
                        | additiveExpr '-' multiplicitiveExpr
        '''
        lhs = p[1]
        rhs = p[3]
        if p[2] == '-':
            rhs = AST(sympy.Mul(sympy.Integer(-1),rhs.sympy), rhs.astUnit)
        p[0] = AST(sympy.Add(lhs.sympy,rhs.sympy), self.checkExactUnits(lhs.astUnit,rhs.astUnit))