April 2022
Beginner to intermediate
486 pages
10h 22m
Chinese
Content preview from 云端基因组学
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274
｜
第
9
章
call
HaplotypeCaller {
input
:
input_bam = select_first([CramToBamTask.output_bam, input_bam]),
...
}
}
由上述
call
语句
input
小节可见，
input_bam
值为另一函数
select_first()
的返回值。
该函数名暗示它负责从已有内容中选择某些内容，而且我们看到它读入一数组的值，
但它到底是什么意思并不十分明确，不是吗？我们若只想让它使用数组第一个元素，
为什么首先要给它数组呢？
是哦，这有点奇怪。这里有个细节要讲下，
select_first()
的设计初衷是容忍缺失值，
该特性在处理条件语句时很有必要：你可能生成某些输出而非其他输出，具体因你
所选路径而异。可是如果你尝试给它们不存在的输出值，大多数
WDL
函数将会失败。
反之
select_first()
仅仅是问：你还有什么其他也许可以使用的值吗？
我们带着这个信息，再详细看下赋值语句。用以下方式表示代码可以切分为几个意
义单元，很方便：
input_bam =
select_first([
CramToBamTask.output_bam , input_bam])
HaplotypeCaller
的输入
文件应是
……
……
来自
CramToBamTask
的输出
……
……
但如其不存在
，
就用原输入文件
。
当工作流执行引擎评估需运行什么任务以及在什么输入
/
输出上运行时，第一个任
务的输出还不存在。第一个任务的输出也许会在稍后的一个时间点被创建 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.