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Casting with parentheses
f#

Hi,

I've been using F# for all of 2 days, so apologies if any of this is blatantly obvious!

I'm trying to use a 3rd party .Net dll within F# and having problems with a particular method (or should I say function?) call. I've been able to create objects and call methods ok, but there's a particular constructor that is confusing me. The description of the constructor is:

Something(paramA: uint32)

so I try and call like I would in C#;

let a = new Something(100)

except that it tells me the parameter is of type int where it should be uint32. I then tried;

let a = new Something(100 :> uint32)

which tells me that the type int is not compatible with the type uint32. In messing around, I tried:

let a = new Something((uint32) 100)

which appears to work, in that it compiles, but I have no idea whether the value actually gets passed to the constructor.

My confusion surrounds the fact that I have no idea why it compiles as it doesn't make any sense from my reading on F#. Also, what should I be doing?

Many thanks for your help.

Ian

.

See

What does this C# code look like in F#? (part one: expressions and statements)

The first section is about casts.

In your case,

((uint32) someValue)

just means

uint32 someValue

or

uint32(someValue)

In all cases, uint32 here is a library function that does numerical conversion.

By on 6/3/2009 10:21 AM ()

Thanks, that makes loads of sense now. So the parentheses just delimit the function, which, in the case above, just returns the function after evaluating?

By on 6/3/2009 10:56 AM ()

In F# integer types are not converted into each other automatically. 100 is constant of type int. To make it be uint32 constant use 'u' suffix, e.g. 100u .

By on 6/3/2009 12:38 PM ()

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