What is best way to get see function from separate file

[Suliman via Digitalmars-d-learn]

>You could pass an argument of type FileLogger (probably better a 
>pointer?)
>foo ( FileLogger log )
>{ }

I like it. Am i right understand that it prevent creation 
unneeded of new instance of logger?

And what problems I can get if I will create new instance of 
logger in every stand alone function? Just resource overusage?