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Expert F# code question
f#book

Hi,

i am reading this excellent book and i have stumbled across a code snippet that does not behave as i expect to:

let urlFilter4 url agent =
match url, agent with
| "[link:abc.com",] 86 -> true
| "[link:def.com",] _ -> false
| _ -> failwith "unexpected input"

let res = urlFilter4 "[link:notexist.com",] 871
System.Console.WriteLine(res)

i expect that res will have the value of "unexpected input" but i has this: "Program+clo@49,871>

I change the res assignment line to something that should return true, like:
let res = urlFilter4 "[link:abc.com",] 86 and i expect rest to have the value of true.
But it gives me something the above-mentioned value...

What am i doing wrong here ??

.

You need to remove the comma between the arguments in your call to res. Your "call" is identical to:

1

let res x = urlFilter4 ("http://notexist.com", 871) x

which is actually not a call, but a function definition.

By on 9/24/2008 10:49 AM ()

At the risk of being pedantic, it's actually

1

let res = (urlFilter4 "http://notexist.com"), 871

where the result 'res' is a tuple of a function and an int.

Either way, the problem is the spurious comma.

(If this is confusing, you might check out

[link:lorgonblog.spaces.live.com]

where I discuss some related issues in more depth.)

By on 9/24/2008 11:17 AM ()

What a dump-head i am some times...

It was indeed that comma. This is what you get if you are brain-stuck to some other languages that you use for quite some time now...

Thanks guys!

By on 9/24/2008 11:55 AM ()

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