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Unary operators in 1.9.1.18
f#

Hello

I got following definition of unary operator:

let (~!@) x = x + "; yummy"

I assume, that ~ sign specifies that operator is unary. When using built-in operator ~- (unary minus) the ~ can be ommited and the operator can used like this:

~-1;; // result is -1

-1;; // result is -1

I would expect that omitting ~ would work for custom operators as well so I could write both following statements:

~!@ "apple";; // result is "apple; yummy"

!@ "apple";; // error: FS0039: The value or constructor '!@' is not defined.

Is there a way ~ character can be ommited? Is this intended behaviour? I use F# 1.9.1.18.

Thanks in advance,

Daniel Balas

.

Hi Daniel,

Your assumption is slightly wrong, F# operators are unary if they have one parameter, it has nothing to do with the ~ sign. The reason you see the behaviour for minus sign is that both ~- and - are defined. I'm not sure why it has two operators for unary minus but I'm guessing ocaml compatablity.

So the answer is if you want both operators to exist then define them both:

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#light
let (~!@) x =  x + "; yummy"
let (!@) x =  x + "; yummy"

~!@ "apple"
!@ "apple"

Cheers,
Rob

By on 8/21/2007 12:54 AM ()

The characters with which a unary operator can start is limited.

See Don's post at

[link:cs.hubfs.net]

By on 8/21/2007 3:15 AM ()

I must have done something wrong, because (!@) alone didn't work. I wonder what led me to this kind of confusion [:)]. Anyways, really thanks.

By on 8/21/2007 1:46 AM ()

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