We don't need to pass in the-string to recurse because it is already in the parent environment and does not change from call to call.

我们不必将the - string传递给recurse，因为它已经在父环境(parent environment)中，而且从一个调用到另一个调用时不会改变。

youdao

In her new incubator, the baby would sit on a heated mattress that would then fold around it creating a closed, sealed environment when held by the parent.

BBC: Baby in an incubator

The parent of America's fourth-largest wireless operator, T-Mobile USA, cited "the extremely competitive environment in Germany and the recent foreign exchange rates development" as reasons for altering its outlook.

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