That idiom is so common, that if the switch value is omitted, it is assumed to be true. So the above could be rewritten as.

这些都是公共的约定俗成，比如如果分支值省略了，就是默认为真，所以上面的代码可以这样写。

youdao

Introduced a type complex press-switch sensor. The sensor can setup many switch value, provide upper-limit, lower-limit and security alarm.

介绍一种复合式压力开关传感器，可设置多路开关量限，提供系统上、下限和超限报警。

youdao

In Bellevue, the switch to adaptive signals has been a lesson in the value of welcoming new approaches.

在贝尔维尤，采用自适应信号灯是接受新方法所带来的一次教训。

youdao

If there becomes reason to question that value, people can switch from dollars to gold currency (most easily through electronic payment systems like debit cards).

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Probably need Switch to get into the mix for the value to be right.

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In Puebla, officials are encouraging farmers to switch from maize and coffee to higher-value crops, such as bamboo and fruit.

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