| -- Retrieve descendants | |
| -- ==================== | |
| -- retrieve descendants of #4 | |
| SELECT c.* | |
| FROM Comments AS c | |
| JOIN TreePaths AS t ON c.comment_id = t.descendant | |
| WHERE t.ancestor = 4; | |
| -- Retrieve ancestors |
| 什么是交易策略？ | |
| 交易策略是一系列规则的集合，包括进场和出场的条件，资金管理和风险控制等。策略有简单和复杂之分，简单的策略通常使用技术指标和价格行为，复杂的策略使用高阶数学和统计模型。通常情况下，我们会认为复杂的模型更优，但实证分析和学术研究表明，复杂的模型往往过度挖掘了历史数据，无法适应剧烈的市场变异，相反简单的模型在长期中更加稳定。 | |
| 交易策略可划分为3个部分：指标（Indicator），信号（Signal）和规则（Rule）。 | |
| 指标用于生成交易信号。计算指标的方法多种多样，可以是经济数据或估值指标（如PE和EBITDA），可以是技术指标（如MACD，RSI，MA），也可以是时间序列模型（ARIMA，GARCH）。技术指标在外汇交易中被广泛使用，它们是价格或成交量的函数，主要用于侦测趋势方向，衡量超买超卖状态，以及判断趋势反转。 | |
| 价格和指标的相互作用形成信号。以均线穿越为例，当5日均线上穿10日均线时买入，当5日均线下穿10日均线时卖出。信号并不局限于买入和卖出，也包含筛子，主要作用是剔除噪音。在均线穿越中，交易员可以增加趋势筛子：只有当价格高于200日均线（上涨趋势），以及5日均线上穿10日均线才做多，如果价格低于200日均线，黄金交叉被视为虚假信号。著名的筛子有趋势筛子，时间筛子，成交量筛子和波动性筛子，它们是信号的重要组成部分。 | |
| echo "Flipping tables! (╯°□°）╯︵ ┻━┻" | |
| num_rules=3 | |
| real=3 # exposed to the ELB as port 443 | |
| test=4 # used to install test certs for domain verification | |
| health=5 # used by the ELB healthcheck | |
| blue_prefix=855 | |
| green_prefix=866 |
##motions
| motion | description |
|---|---|
| h | Count characters left |
| l | Count characters right |
| ^ | To the first character of the line |
| $ | To the last character of the line |
| f<char> | To the counth character occurrence to the right. F<char> to the counth character occurrence to the left |
| t<char> | To 1 character just before the counth character occurrence to the right |
| T<char> | To 1 character just before the counth character occurrence to the left |
| local redis_c = require "resty.redis" | |
| local ok, new_tab = pcall(require, "table.new") | |
| if not ok or type(new_tab) ~= "function" then | |
| new_tab = function (narr, nrec) return {} end | |
| end | |
| local _M = new_tab(0, 155) |
| #!/bin/bash | |
| # options: | |
| # remove stopped containers and untagged images | |
| # $ dkcleanup | |
| # remove all stopped|running containers and untagged images | |
| # $ dkcleanup --reset | |
| # remove containers|images|tags matching {repository|image|repository\image|tag|image:tag} | |
| # pattern and untagged images | |
| # $ dkcleanup --purge {image} |
| # Start the old vagrant | |
| $ vagrant init centos-6.3 | |
| $ vagrant up | |
| # You should see a message like: | |
| # [default] The guest additions on this VM do not match the install version of | |
| # VirtualBox! This may cause things such as forwarded ports, shared | |
| # folders, and more to not work properly. If any of those things fail on | |
| # this machine, please update the guest additions and repackage the | |
| # box. |
| "20091020 | |
| let mapleader=";" | |
| " " " 映射 | |
| " " 页面操作 | |
| " 一次移动5行 | |
| noremap j 5j | |
| noremap k 5k | |
| " 上下滚动 |
