To support closures fully, a language needs to provide support for manipulating, invoking, and creating functions at run time and for functions to capture the environment in which they were created.
要完全支持闭包，这种语言必须支持在运行时操纵、调用和创建函数，还要支持函数可以捕获创建这些函数的环境。
The only difficulty is that few language run-time libraries currently support full-blown VFS.
最大的困难就是当前支持成熟的VFS的语言运行时库很少。
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