What is the difference between the generic signifier ' and the symbol ^ In F# method signatures -

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i understand tick signify generic parameter, in:

seq.append : seq<'t> -> seq<'t> -> seq<'t>

but caret signify, in:

seq.average : seq<^t> -> ^t

the detailed signature is:

seq.average : seq<^t> -> ^t (requires ^t static member (+) , ^t static member dividebyint , ^t static member zero)

unlike seq.append, seq.average needs more constraints on type of elements. particularly:

                                _ dividebyint (s1 + s2 + ... + sn) n n <> 0 seq.average {s1; s2;...; sn} = /                                \_ ^t.zero n = 0

as can see, both (+), dividebyint , zero required in order seq.average<^t> makes sense.

useful information generics found heremsdn.


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