Create README.md

README.md

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+# fsharp-vectors
+
+Type-safe vectors in F#.
+
+# What?
+
+```fsharp
+let l1 = [ 1 ; 2 ]
+let l2 = [ 3 ]
+List.zip l1 l2
+|> ignore
+```
+
+Oh no! Lists aren't safe!
+
+```fsharp
+let v1 = 1 ** 2 ** -()
+let v2 = 1 ** ()
+Vector.zip v1 v2 // doesn't compile!
+|> ignore
+```
+
+# How?
+
+Peano encoding of the naturals, basically.
+We define a type `Z` and a type `S : * -> *`, and interpret `S Z` as the number 1.
+
+# Syntax
+
+I refuse to apologise for the syntax.
+
+* `Vector.empty` can also be written `-()`. (It's actually an overload of the unary `-`.)
+* `Vector.cons` can also be written `**`. (It had to be this way because we need right-associativity, and not that many symbols in F# have right-associativity.)
+
+# Efficiency
+
+These things are actually not that bad at runtime, although on no account should you use `VectorCrate` on the hot path.
+I have yet to do any benchmarking, but I think they'll be pretty good.