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Array.zeroCreate and type inference
f#

I had some code like:

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let row = Array.zeroCreate numS

// ...

row.[0] <- 1

and it never really occurred to me that this is odd until I added some similar code next to it:

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let row2 = Array.zeroCreate numS

// ...

row2.[0] <- false

I thought type inference in F# was left-to-right, top-to-bottom. What am I missing here?

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An interesting code snippet.

For anyone else looking at it, this bit of formatting might help...

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let row = Array.zeroCreate 5
row.[0] < -1


let row2 = Array.zeroCreate 5
row2.[0] < false

In an .fs file it's fine. Pasted line by line into fsi there is an error after the first line. if pasted in a block, it's OK, and returns...

val row : int [] = [|0; 0; 0; 0; 0|]
val row2 : bool [] = [|false; false; false; false; false|]

By on 12/4/2009 6:50 PM ()

It is, but it can float constraints to get solved later. In this case the array has type array<'a> after the first line, and then later when you assign it can pin down 'a to be bool or int.

By on 12/3/2009 9:55 AM ()

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