Re: destructuring let and for
Thanks for the answer, I'll try to do as you suggest.
Thanks
On Tuesday, June 10, 2014 11:51:59 PM UTC+2, Paul G wrote:
>
> Hi Francesco,
>
> I apologize for using "for" earlier, as I did not explain how you should
> be using it. The comment of "do something with rel" should have indicated
> that it resolved to an expression, and those expressions would be returned
> in a seq (the "for" expression resolves to have a value of a seq).
>
> Given your last example, I could read it a couple of ways. My first
> interpretation is that you just need a way to convert names to nodes, and
> then to connect all the nodes. My preference would be to separate these
> steps, so the conversion would be done with:
>
> (map convert-to-node list-of-names)
>
> The result of this is then looped through to create the relations (as in
> my previous example, the relations are both ways, and not reflexive):
>
> (let [nodes (map convert-to-node list-of-names)]
> (for [node1 nodes, node2 nodes :when (not= node1 node2)]
> (nrl/create conn page1 page2 :links)))
>
> This creates a seq of all the relations, in both directions. So one
> relationship will be [Jupiter->Pluto] and another will be [Pluto->Jupiter].
> To create one-way relationships, I suggest the use of indexes, as in my
> previous post.
>
> However, when I followed your link to the example data, I see that there
> are connections between some nodes and not others. In that case it would be
> preferable to create a mapping of names to nodes, and then as the
> relationships are required those nodes can be found easily:
>
> (def create-nodemap [names]
> (zipmap names (map convert-to-node names)))
>
> Now you can grab the nodes as needed to work with them:
>
> (defn connect [nodemap name1 name2]
> (nrl/create conn (nodemap name1) (nodemap name2 :link)))
>
> (let [nodemap (create-nodemap ["jupiter" "hercules" "neptune" "pluto"])]
> (connect nodemap "jupiter" "hercules" :link)
> (connect nodemap "jupiter" "neptune" :link)
> (connect nodemap "jupiter" "pluto" :link)
> (connect nodemap "neptune" "pluto" :link))
>
> I am avoiding many tricks here that I'd use in reality, to avoid making it
> too obscure.
>
> Note that the above has links between Juptier, Neptune and Pluto, but
> Hercules is only linked to Jupiter. So we don't have everything connected
> to everything else. However, this approach is only useful in simple
> examples like this, since any real data set would be too large to write
> code for every connection. Instead, the actual data (coming from a csv
> file, or something) would be read and used to create the connections.
>
> What does your original data look like? Are you just trying to re-create
> the graph you linked to, or is the data available in some structured format?
>
> Paul
>
>
>
> On Tue, Jun 10, 2014 at 4:08 PM, Francesco Lunelli > wrote:
>
>> Thanks for the answer.
>> If I understand well your code it's a partial answer to my question
>> because if I'm not wrong it creates a link between to elements at a time.
>> What I need is to create all the elements then create on them every kind of
>> relation.
>> I take as example a graph db used in another engine
>> https://raw.githubusercontent.com/wiki/thinkaurelius/titan/images/graph-of-the-gods-2.png
>> Here you have a graph of Roman gods, with the name of the gods and the
>> links among them. So if I have for example a list of the names of Roman
>> gods I need to create all the nodes, then connect them in various mode.
>> I want to take the list '("jupiter" "saturn" "hercules" "neptune" "pluto"
>> ...) and cycling on it I want to creare the nodes. When I finished to
>> create them I need to be able to call every node to crete the various links
>> among them. For example I need to link jupiter with pluto, jupiter with
>> neptun, neptun with pluto and so on.
>>
>> Thanks
>>
>> Francesco
>>
>>
>> On Tuesday, June 10, 2014 7:43:21 PM UTC+2, Paul G wrote:
>>
>>> Hi Francesco,
>>>
>>> You want to decouple your code from the data that it is operating on, so
>>> your code can operate regardless of the contents of the list. Otherwise,
>>> you'll need code that matches the list, in which case it could all be code
>>> anyway. Operating on arbitrary lists makes it easy to test simple examples
>>> too.
>>>
>>> A
Re: destructuring let and for
Thanks for the answer.
If I understand well your code it's a partial answer to my question because
if I'm not wrong it creates a link between to elements at a time. What I
need is to create all the elements then create on them every kind of
relation.
I take as example a graph db used in another
engine
https://raw.githubusercontent.com/wiki/thinkaurelius/titan/images/graph-of-the-gods-2.png
Here you have a graph of Roman gods, with the name of the gods and the
links among them. So if I have for example a list of the names of Roman
gods I need to create all the nodes, then connect them in various mode.
I want to take the list '("jupiter" "saturn" "hercules" "neptune" "pluto"
...) and cycling on it I want to creare the nodes. When I finished to
create them I need to be able to call every node to crete the various links
among them. For example I need to link jupiter with pluto, jupiter with
neptun, neptun with pluto and so on.
Thanks
Francesco
On Tuesday, June 10, 2014 7:43:21 PM UTC+2, Paul G wrote:
>
> Hi Francesco,
>
> You want to decouple your code from the data that it is operating on, so
> your code can operate regardless of the contents of the list. Otherwise,
> you'll need code that matches the list, in which case it could all be code
> anyway. Operating on arbitrary lists makes it easy to test simple examples
> too.
>
> A simple way to create links between pages might be like this (assuming
> that conn is in scope and initialized):
>
> (for [list-elt1 the-list, list-elt2 the-list :when (not= list-elt1
> list-elt2)]
> (let [page1 (page-fn list-elt1)
> page2 (page-fn list-elt2)
> rel (nrl/create conn page1 page2 :links)]
> ;; do something with rel
> ))
>
> This creates links both ways.
>
> If you only want one-way links then the first approach that comes to mind
> (there are others, and they're probably better) is to index through the seq:
>
> (for [n (range (count the-list)), m (range (inc n) (count the-list))]
> (let [page1 (page-fn (nth the-list n))
> page2 (page-fn (nth the-list m))
> rel (nrl/create conn page1 page2 :links)]
> ;; do something with rel
> ))
>
> The general idea here is to use an arbitrary var to represent your list
> elements and pages.
>
> Does this address your issue?
>
> Regards,
> Paul
>
>
>
> On Tue, Jun 10, 2014 at 1:04 PM, Francesco Lunelli > wrote:
>
>> Thanks for the answer, I try to explain better what I have to do.
>>
>> I need to create some nodes in Neo4j then I need to create relationships
>> between those nodes.
>>
>> This is an example taken from necons doc.
>>
>> (let [conn (nr/connect "http://localhost:7474/db/data/";)
>> page1 (nn/create conn {:url "http://clojurewerkz.org"})
>> page2 (nn/create conn {:url "http://clojureneo4j.info"})
>> ;; a relationship that indicates that page1 links to page2
>> rel (nrl/create conn page1 page2 :links)]
>> (println rel)))
>>
>> They create two nodes called page1 and pag2 then connect them.
>>
>> In my case I have a list of names, I want to create one node for each of
>> them with the possibility to work on nodes after they are created.
>> So if I have for example a list like this one (def mylist '(j"john"
>> "paul" "mary")) I want to create three nodes calling them john paul and
>> mary storing the value "John" "Paul" "Mary" and after having created them I
>> want to be albe to connect nodes creating a relationship among them, with a
>> funciont like rel (nrl/create conn john paul :friend)]
>>
>> I hope this example explain better my needs.
>>
>> Thanks in advance
>>
>> Francesco
>>
>>
>> On Tuesday, June 10, 2014 6:11:16 PM UTC+2, James Reeves wrote:
>>
>>> Could you explain a little more what your end goal is?
>>>
>>> It sounds like you want a map, but without knowing more about the
>>> purpose, it's difficult to say.
>>>
>>> - James
>>>
>>>
>>> On 10 June 2014 16:43, Francesco Lunelli wrote:
>>>
>>>> Hello everybody, I have a newbie question about destructuring and
>>>> assigning and didn't find an answer in documentation or books.
>>>>
>>>> I have a list that contains an arbitrary number of elements for example
>>>> '("one" "two" "three" ...) I now only that elements are strings.
>>>>
>>>> I
Re: destructuring let and for
Thanks for the answer, I try to explain better what I have to do.
I need to create some nodes in Neo4j then I need to create relationships
between those nodes.
This is an example taken from necons doc.
(let [conn (nr/connect "http://localhost:7474/db/data/";)
page1 (nn/create conn {:url "http://clojurewerkz.org"})
page2 (nn/create conn {:url "http://clojureneo4j.info"})
;; a relationship that indicates that page1 links to page2
rel (nrl/create conn page1 page2 :links)]
(println rel)))
They create two nodes called page1 and pag2 then connect them.
In my case I have a list of names, I want to create one node for each of
them with the possibility to work on nodes after they are created.
So if I have for example a list like this one (def mylist '(j"john" "paul"
"mary")) I want to create three nodes calling them john paul and mary
storing the value "John" "Paul" "Mary" and after having created them I want
to be albe to connect nodes creating a relationship among them, with a
funciont like rel (nrl/create conn john paul :friend)]
I hope this example explain better my needs.
Thanks in advance
Francesco
On Tuesday, June 10, 2014 6:11:16 PM UTC+2, James Reeves wrote:
>
> Could you explain a little more what your end goal is?
>
> It sounds like you want a map, but without knowing more about the purpose,
> it's difficult to say.
>
> - James
>
>
> On 10 June 2014 16:43, Francesco Lunelli > wrote:
>
>> Hello everybody, I have a newbie question about destructuring and
>> assigning and didn't find an answer in documentation or books.
>>
>> I have a list that contains an arbitrary number of elements for example
>> '("one" "two" "three" ...) I now only that elements are strings.
>>
>> I need to to take every element and use it as the name of a variable
>> inside a let and assign the result of a funcion on that element to that
>> variable.
>> Somthing like this for example:
>>
>> (let [one (clojure.string/capitalize "one")
>> two (clojure.string/capitalize "two")
>> three (clojure.string/capitalize "three")]
>> ;; here I have access to vars one two three etc.
>> )
>>
>> where the names of the vars are taken from the list and values are
>> obtained applying a function on the corresponding element of the list (the
>> capitalize function il only an example, it could be everything else).
>>
>> If I do in this way
>> (for [word ["the" "quick" "brown" "fox"]] (let [word
>> (clojure.string/capitalize word)] (prn word)))
>> it works, but I need to access the variables outside of the cycle for,
>> after having defined and assigned everyone because I need to put in
>> relation some of them.
>>
>> Thanks to everybody
>>
>> Francesco
>>
>>
>>
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>
>
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destructuring let and for
Hello everybody, I have a newbie question about destructuring and assigning
and didn't find an answer in documentation or books.
I have a list that contains an arbitrary number of elements for example
'("one" "two" "three" ...) I now only that elements are strings.
I need to to take every element and use it as the name of a variable inside
a let and assign the result of a funcion on that element to that variable.
Somthing like this for example:
(let [one (clojure.string/capitalize "one")
two (clojure.string/capitalize "two")
three (clojure.string/capitalize "three")]
;; here I have access to vars one two three etc.
)
where the names of the vars are taken from the list and values are obtained
applying a function on the corresponding element of the list (the
capitalize function il only an example, it could be everything else).
If I do in this way
(for [word ["the" "quick" "brown" "fox"]] (let [word
(clojure.string/capitalize word)] (prn word)))
it works, but I need to access the variables outside of the cycle for,
after having defined and assigned everyone because I need to put in
relation some of them.
Thanks to everybody
Francesco
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