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type coercion of int to int64

In the following example, I am calling through to a C# method "BarOfSize" which takes a float.

When I try to pass the result of 1 |> days, I can not get the result of the function to be coerced up to an int64, I have to cast it like below (at least so visual studio claims.)

Is this correct? I thought the type coersion rules should work here?

let days num = num * 86400
let mm num = num * 1000000.

let spec = {
DataRequests = [Series.BarOfSize(int64(1 |> days))];
StartDate = new DateTime(1, 1, 1);
EndDate = DateTime.Now;
InitialCashAllocation = 100. |> mm;
};

Lastly, as an aside, is there is more elegant way to build up my little multiplier abstractions? I suppose i could use extensions to do 1.days or 100.mm - anyone have strong views (backed by actual logic) on which is better?

.Reply

There are very few implicit conversions in F#, you must explicitly convert most data types.

You should have a look at units of measure, though I am unclear how applicable it is to your domain:

[link:blogs.msdn.com]

By brianmcn on 2/24/2009 10:16 PM (permalink)Reply

I see. I was checking this out earlier and it seemed like - according to the "upcasts and downcasts" section - there is some coercion for arguments to a function.

just a stab in the dark, but could the issue be that there is coercion for arguments but not return values that are used in the context of an expression that takes that return value as an argument to an ungeneralized C# method?

By bradford.n.cross on 2/24/2009 10:40 PM (permalink)Reply

No, a closer approximation is that "F# will sometimes upcast through a class hierarchy for you (e.g. you can pass a Cat to a method expecting an Animal), but that's about it." F# will never implciitly convert e.g. an 'int' to an 'int64'.

By brianmcn on 2/24/2009 10:44 PM (permalink)Reply

<dumb> of course.</dumb>

sorry man, its late. nice lambda cats, btw.

By bradford.n.cross on 2/24/2009 11:16 PM (permalink)Reply