I've never seen it before either, it is surprising that this documentation doesn't appear to define it.

The backtick ` appears to be a sigil the author is using for a recursively-defined type, while the a appears to be simply a variable name: "let `a be any recursively defined type, then Ref[`a] declares a reference to that same type".

In reply to Re: Unusual style of documentation? by hv
in thread Unusual style of documentation? by LittleJack

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