var:-value}: If exists and isn't NULL, return 's value.
${var:-value}：如果存在且不是NULL，就返回 的值。
Fang Wencong in her life has vanished, actually as if exists by one special way.
方文从她的生活中消失了，却似乎又以一种特殊的方式存在着。
Need to check if an active market exists for the asset and liability and if exists we must be aware of pricing assumptions used by market participants.
需要检查是否存在活跃市场的资产和负债，如果存在，我们必须意识到定价市场参与者所使用的假设。
While physicists have demonstrated entanglement with specially prepared atoms, no-one knows if it also exists between atoms making up human minds.
尽管物理学家已经证明了特制原子之间存在纠缠，但没人知道它是否也存在于组成人类思维的原子之间。
If no drainage system exists, the water table rises, bringing dissolved salts to the surface.
如果没有排水系统，地下水位就会上升，把溶解的盐带到地表。
If only one album exists anyhow, I just take it.
总之，如果只存在一个唱片，我就选择它。
If the pattern exists on only one run-time, that can help you in making your decision.
如果该模式仅在一个运行时上存在，则可以帮助您做出决策。
If the WPS_HOME directory exists then delete it and its contents.
如果WPS_HOME目录存在，那么删除它和其中的内容。
If the WAS_HOME directory exists then delete it and its contents.
如果WAS_HOME目录存在，那么删除它和其中的内容。
If the entry exists, it would be in the name service representation format.
如果条目存在，它应该是名称服务表示格式的。
If an entry exists, then delete the line containing the entry.
如果该条目存在，则删除包含的该条目的语句。
The problem is that if life exists elsewhere in the solar system it must be living underground on places like Mars, Europa, and Enceladus.
问题是如果有生命存在在太阳系的其它地方，那他一定是生活在像火星，欧罗巴和恩克拉多斯的地下。
If no baseline exists, counters are relative to database activation.
如果基线不存在，计数器值相对于数据库激活时。
If it exists the new planet is so freezing cold it is difficult to spot, researchers said.
研究人员说，如果存在如此寒冷的新行星，那么将很难认出它。
If the file exists, the installer creates a backup before making the changes.
如果该文件存在，安装程序在更改前会创建一个备份。
If it exists, it could explain literally everything in the universe - from subatomic particles to the laws of speed and gravity.
如果这些弦真的存在，基本上就可以解释宇宙中所有的存在——从亚原子粒子到速度和重力定律。
If the queue already exists, its handle is returned.
如果队列已经存在，返回其句柄。
The Higgs boson is a hypothesised particle which, if it exists, would give the mechanism by which particles acquire mass.
希格斯玻色子是一个假说中的粒子。如果它存在，我们就知道了赋予粒子以质量的物理机制。
If life exists, scientists expect the planet's rays to be embedded with tell-tale chemical fingerprints of atmospheric molecules, such as oxygen and methane.
如果生命存在，科学家们希望这个行星上的光线能够嵌入大气层分子的化学指纹位移指示器，像氧气、甲烷一类的气体。
Mars is a focal point in the quest to learn if life exists beyond Earth.
火星是研究地球以外是否存在生命的一个焦点。
“If God exists, he’s really got it in for Haiti, ” Pooja Bhatia, a journalist who lives in Haiti, wrote in the Times.
“如果上帝真的存在的话，他也是真地在存心对付海地人民”，居住在海底的新闻记者普伽.巴迪亚在《泰晤士报》上写道。
Second question, though, is: Does the soul, even if it exists, survive the destruction of the body?
第二个问题，如果灵魂存在，能否在身体毁坏后得以幸存？
Knowing if God exists, or not.
认知神的存在与否。
If it exists at all, it makes up about three-quarters of the stuff in the universe.
如果它真的存在，它会占据宇宙四分之三的物质。
We have other hints about the Higgs; for example, if it exists, it plays a role in "unifying" different forces.
我们还有希格斯粒子的其他线索。举例来说，如果它存在，那么它在“统一”不同种类的力之中(译者注，大一统理论)也有作用。
If one exists, it is pulled and used.
如果存在，就将其调出使用。
As you can see, F4 (if it exists) is constant, and hence trivially predictable.
正如您所看到的，F4(如果它存在的话)是常量，因此可以进行琐碎的预测。
If one exists, the PresenceSession calls the notify method of the associated PresenceListener to deliver the notification.
如果存在一个新通知，PresenceSession将调用相关PresenceListener的notify方法来交付通知。
If it exists, it sees if it is atom.
如果存在该参数，就判断它是否是atom。
This will create a TDS physical format called Text_IDoc if none exists.
这将创建名为Text_IDoc的tds物理格式(如果还不存在的话)。
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