Thank you, Meikel and Christian!
- Srini
On Mar 9, 7:43 am, Christian Vest Hansen <karmazi...@gmail.com> wrote:
> On Tue, Mar 9, 2010 at 6:26 AM, Srini <devfac...@gmail.com> wrote:
> > Hi. I am completely new to clojure - my 3rd day or so. Need to go buy
> > a book on the subject. So please help me with a couple of things:
>
> > Item 1) I have two calls to count. One works, and the other does not.
>
> > ; counts number of items in collection
> > user=> (count (list 1 2 3 4 "er" 34) )
> > 6
>
> > ; count does not work. I get an exception. Need to figure out what I
> > am doing wrong here.
> > user=> (count (list 23 "3er" oel" 5) )
> > java.lang.Exception: EOF while reading string
>
> You are missing a double-quotation character before eol"
>
>
>
>
>
>
>
> > Item 2) I see from the documentation that the contains? function (it
> > is a function, right? just want to be sure. this is my 2nd or 3rd day
> > learning about clojure.) returns true if key is present in collection.
> > And there is a reference in the online docs to "numerically indexed
> > collections like vectors and Java arrays". In the following examples,
> > the first one works as I expected. But the second one does not work as
> > I thought. How do I check if an item is in a list?
>
> > ; does the vector contain index 0?
> > user=> (contains? [1 2 3 4] 0)
> > true
>
> > ; could not get it to work for lists. apparently works only for
> > numerically indexed collections like vectors.
> > ; doesn't throw an exception either. "intuitively", I think the
> > following should have returned true.
> > user=> (contains? (list "3e" "2 tired" "1 more") "3e" )
> > false
>
> I think contains? only work on things that are associative:
>
> user=> (associative? [])
> true
> user=> (associative? (list))
> false
>
> So a list is not associative, as it has no (near) constant-time way of
> looking up things in it by index, key or value.
>
> Maybe you want to use a set instead of a list:
>
> user=> (contains? #{"3e" "2 tired" "1 more"} "3e" )
> true
>
>
>
>
>
>
>
> > Your help is much appreciated.
>
> > Thank you for your time. - Srini
> > As an aside, I guess I am approaching this as I have regular
> > procedural languages like C, C++, Java, C#, VB, and my all-time
> > favourite so far - Python, etc. And its taking a different kind of
> > thinking to even understand the basics of closure since its just so
> > different from the others. I am recording my learning experiences in
> > my very first blog ever :)http://closurefp.blogspot.com/Hopefully it
> > will help someone.
>
> > --
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>
> --
> Venlig hilsen / Kind regards,
> Christian Vest Hansen.
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