what is the mean that call function start with a dot.

[Paul Backus]

On Sunday, 22 September 2019 at 04:15:53 UTC, lili wrote:
> Hi：
>    yesterday I saw some d code， where is an .fn() call syntax, 
> what is it mean.

It means that `fn` is looked up in the module's top-level scope.

Source: https://dlang.org/spec/expression.html#identifier