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Operator ??
f#

Hi,

It seems the operator ?? is currently used for a deprecated language construct that tests for null and if null returns a default value, just like the identically named operator in C#. I'd love to be able to use that operator with options instead, i.e. as if it was defined as

let (??) opt d =
match opt with
| Some v -> v
| None -> d

With this definition one could write
let v = arg ?? 1
instead of
let v = match arg with Some v -> v | None -> 1

Is there a chance that such a definition gets into fslib or that the operator name ?? is "unreserved"?

.

I don't know about operator ?? but the defaultArg function can be used in place of the match currently.

By on 4/12/2008 3:20 AM ()

Hi Julien,

I didn't notice that defaultArg became part of fslib, thanks for the hint.

You've got to admit, though, that `a ?? v` is more readable than `a defaultArg b`, not only because it's terser and doesn't clutter up longer expressions, but also because it stands out from normal expressions and immediately signals "a is an option type".

Given that option types are ubiquitous in typical F# code and that there is a precedent for a very similar operator in C#, wouldn't such a definition of ?? be a good fit for F#?

By on 4/12/2008 3:46 AM ()

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