Notation question

[Juan Carlos Arevalo Baeza]

    Just a very naive question, because I'm really curious. I've seen in 
previous messages here discussions about type systems using this kind of 
notation:

>  G |- f :: all x::S . T   G |- s :: S
>--------------------------------------
>          G |- f s :: [s/x]T

    I'd never seen it before, and a few searches I've launched over the net 
have turned up just a couple more examples of this notation, but without a 
single reference to how it works or what it means, or even what it's 
called, for that matter.

   I'd appreciate any pointers.


    Salutaciones,
                               JCAB

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