For work, I want to describe the format of a standard medical formular (used to report drugs side-effects) the most concise way. (Roughly, to render it afterwards through hiccup but not only, that's why I don't write it directly as a hiccup structure)
For instance, part of the description would be:
{"reportertitle" [:one-of "Dr" "Pr" "Mrs" "Mr"] ; the reporter is usually the physician
"reportergivenname" :text
"reporterfamilyname" :text
"reporterorganization" :text
"reporterdepartment" :text
....
"literaturereference" :text
"studyname" :text
....}
The keys are standard names, I cannot change them, but I'd like to be able to easily factorize things: for instance the prefix "reporter" is highly used throughout the map, I would like to be able to factorize it, for instance by doing:
{ (prefix "reporter"
"title" [:one-of "Dr" "Pr" "Mrs" "Mr"]
"givenname" :text
"familyname" :text
"organization" :text
"department" :text)
.....
"literaturereference" :text
"studyname" :text
....}
But this cannot work, because I think I cannot "integrate" (splice, I believe is the correct term) the result of 'prefix', be it a function or a macro, inside the outer map.
Is there a solution to achieve this while maintaining a high level of declarativity/conciseness? (the whole form is huge and might be read by non-developers)
(As I'm new to Clojure, pretty much every design suggestion is welcome ;) )
Thanks!
You are right in that a macro cannot tell eval to splice its result into the outer expression. A straightforward way around it would be to wrap the whole map definition in a macro that recognizes the prefix expressions and translates them into appropriate key-value sequences inside the resulting map definition.
You can also do it with functions only by just gluing the submaps with merge:
(defn pref-keys [p m] (apply hash-map (apply concat (for [[k v] m] [(str p k) v])))))
(merge
(pref-keys "reporter"
{"title" [...]
"givenname" :text
...})
{"literaturereference" :text
"studyname" :text})
Which might be a bit more verbose but probably also a bit more readable.
Edit: There is one more limitation: map literals are created before any macros (inside or outside ones) are evaluated. A macro whose argument is a map literal will get a map, not some form whose evaluation would eventually produce the map. Of course the keys and values in this map are unevaluated forms, but the map itself is a proper map (IPersistentMap).
In particular this means that the literal needs to contain an even number of forms, so this:
(my-smart-macro { (prefix "reporter" ...) } )
will fail before my-smart-macro has a chance to expand the prefix. On the other hand, this will succeed:
(another-macro { (/ 1 0) (/ 1 0) })
... provided the macro filters out the invalid arithmetic expressions from its input map.
This means that you probably do not want to pass a map literal to the macro.
In advance, I should say that this answer may not at all be what you are looking for. It would be a way of doing things that would totally alter your data structure, and you seem to maybe be saying that that's not something you can do. Anyways, I'm suggesting it because I think it would be a good change to your data structure.
So, here's how I propose you re-envision your data:
{:reporter {:title "Dr, Pr, Mrs, or Mr here"
:given-name "text here"
:family-name "text here"
:organization "text here"
:department "text here"
...}
:literature-reference "text here"
:study-name "text here"
...}
There are two changes I'm putting forth here: one is structural and the other is "cosmetic". The structural one is to nest another map in there for the reporter-related stuff. I personally think this makes the data clearer, and it is no less accessible. Instead of doing something like (get *data* "reportertitle") to access it, and (assoc *data* "reportertitle" *new-title*) to make a new version of it, you would instead to (get-in *data* [:reporter :title]) and (assoc-in *data* [:reporter :title]).
The cosmetic change is to turn those string-based keys into Clojure keywords. My main reasons for suggesting this are that it would be more idiomatic and that it would be potentially clearer to read your code. For a better discussion on why to use keywords see maybe here or here.
Now, I realize everything I've said pre-supposes that you actually can change how your data is structured and how the keywords are named. You said "The keys are standard names, I cannot change them", and this seems to indicate that this type of solution wouldn't work for you. However, maybe you could inter-convert between the two forms. If you are importing this data from somewhere and it already has the format that you give above, you would convert it into the nested-map-with-keywords form, and keep it that way while you did whatever you did with it. Then, when you export the data to actually be outputted or used (or whatever ultimate end it serves), you would convert it back to the form as you have it above.
I should say that I, personally, do not at all like this "inter-conversion" idea. I think it divides the notions of "code" and "data", which seems like such a shame considering it would be done only to have the code "look and feel nicer" than the data. That being said, I'm proposing it in case it sounds good to you.
Related
I am passing a vector of hiccup to a funtion that just wraps it in more hiccup, but it does not return it as I would expect.
Here's an example of what I mean:
(defn wrap-fn
[input]
[div.content-box
[input]])
(defn main-fn
[vector-of-hiccup]
(foreach [hiccup from vector-of-hiccup]
(wrap-fn hiccup-from-list)))
How do I implement the made up foreach loop above?
I've tried to use 'apply' to apply the wrap-fn to each of the vector params but it only returns the first element wrapped. I've tried to creating all sorts of loops and I have similar levels of success.
I'm sure there is a way to do this, please help me find one that works.
You need something like this:
(defn wrap-fn
[input]
[:div.content-box
[input]]) ; <= you may not want to wrap `input` in a vector.
(defn main-fn
[vector-of-hiccup]
(vec
(for [item vector-of-hiccup]
(wrap-fn item))))
Note the : in :div. Hiccup vectors always start with a keyword. Also, since for returns a lazy sequence, you should convert it into a vector with vec.
Also, depending on your situation, you may want to have input instead of [input] under the :div.content-box.
See the Documentation section of the clj-template project for valuable learning information.
for an assignment I need to create a map from a text file in clojure, which I am new to. I'm specifically using a hash-map...but it's possible I should be using another type of map. I'm hoping someone here can answer that for me. I did try changing my hash-map to sorted-map but it gave me the same problem.
The first character in every line in the file is the key and the whole line is the value. The key is a number from 0-9999. There are 10,000 lines and each number after the first number in a line is a random number between 0 and 9999.
I've created the hashmap successfully I think. At least, its not giving me an error when I just run that code. However when I try to iterate through it, printing every value for keys 0-9999 it gives me a stack overflow error right at the middle of line 2764(in the text file). I'm hoping someone can tell me why it's doing this and a better way to do it?
Here's my code:
(ns clojure-project-441.core
(:gen-class))
(defn -main
[& args]
(def pages(def hash-map (file)))
(iter 0)
)
(-main)
(defn file []
(with-open [rdr (clojure.java.io/reader "pages.txt")]
(reduce conj [] (line-seq rdr))))
(defn iter [n]
(doseq [keyval (pages n)] (print keyval))
(if (< n 10000)
(iter (inc n))
)
)
here's a screenshot of my output
If it's relevant at all I'm using repl.it as my IDE.
Here are some screenshots of the text file, for clarity.
beginning of text file
where the error is being thrown
Thanks.
I think the specific problem that causes the exception to be thrown is caused because iter calls itself recursively too many times before hitting the 10,000 line limit.
There some issues in your code that are very common to all people learning Clojure; I'll try to explain:
def is used to define top-level names. They correspond with the concept of constants in the global scope on other programming languages. Think of using def in the same way you would use defn to define functions. In your code, you probably want to use let to give names to intermediate results, like:
(let [uno 1
dos 2]
(+ uno dos)) ;; returns 3
You are using the name hash-map to bind it to some result, but that will get in the way if you want to use the function hash-map that is used to create maps. Try renaming it to my-map or similar.
To call a function recursively without blowing the stack you'll need to use recur for reasons that are a bit long to explain. See the factorial example here: https://clojuredocs.org/clojure.core/recur
My advice would be to think of this assignment as a pipeline composed of the following small functions:
A function that reads the lines from the file (you already have this)
A function that, given a line, returns a pair: the first element of the pair is the first number of the line, the second element is the whole line (the input parameter) OR
A function that reads the first number of the line
To build the map, you have a few options; two off the top of my mind:
Use a loop construct and, for each line, "update" the hash-map to include a new key-value pair (the key is the first number, the value is the whole line), then return the whole hash-map you've built
Use a reduce operation: you create a collection of key-value pairs, then tell reduce to merge, one step at a time, into the original hash-map. The result is the hash-map you want
I think the key is to get familiar with the functions that you can use and build small functions that you can test in isolation and try to group them conveniently to solve your problem. Try to get familiar with functions like hash-map, assoc, let, loop and recur. There's a great documentation site at https://clojuredocs.org/ that also includes examples that will help you understand each function.
TL;DR: Is the following a good pattern for a library?
(def ^{:dynamic true} *var*)
(defn my-fn [{:keys [var]}]
(do-smth (or var *var*)))
--
Say I want to write a sentiment analysis library.
Is it good design in get-sentiment fn to accept optional sentiment labels but provide default one as dynamic var?
(def ^:dynamic *sentiment-level-labels*
["Very Negative" "Negative" "Neutral" "Positive" "Very Positive"])
;;...
(defn get-sentiment-scores
"Takes text and gives back a 0 to 4 sentiment score for each sentences."
[text]
;;...)
(defn get-sentiment
"Gives back a sentiment map with sentences scores,
average score, rounded score and labeled score.
Can accepts custom sentiment level labels under :labels opt."
[text & {:keys [labels]}]
(let [scores (get-sentiment-scores text)
average-score (get-average scores)
rounded-score (Math/round average-score)
label (get (or labels *sentiment-level-labels*) rounded-score)]
{:scores scores
:average-score average-score
:rounded-score rounded-score
:label label}))
Clojure library coding standards official page says:
If you present an interface that implicitly passes a parameter via
dynamic binding (e.g. db in sql), also provide an identical interface
but with the parameter passed explicitly.
https://dev.clojure.org/display/community/Library+Coding+Standards
In my example, I provided only one interface but with opt argument.
Is this okay? Are there better ways to handle this?
Thank you!
Dynamic vars are full or pitfalls. They push your API code towards implicit environmental coupling, and often force your calling code to add a lot of (binding ...) clauses, which kind of defeats the purpose of concision for using Dynamic vars in the first place. They also lead to tricky edge cases if control is passed from one thread to another.
In your case, I would recommend simply passing the labels in a params map argument:
(def default-sentiment-level-labels
["Very Negative" "Negative" "Neutral" "Positive" "Very Positive"])
(defn get-sentiment
"Gives back a sentiment map with sentences scores,
average score, rounded score and labeled score.
Can accepts custom sentiment level labels under :labels opt."
[text {:as params, :keys [labels] :or {labels default-sentiment-labels}}]
...))
Note that the usage of a map can be interesting, because a map is opaque to intermediaries: you can have various components of your algorithm read only from the params map the keys that concern them.
I have 2 maps:
(def look {"directions" :look
"look" :look
"examine room" :look
})
(def quit {"exit game" :quit
"quit game" :quit
"exit" :quit
"quit" :quit
})
which are merged into one map by:
(defn actions [] (merge look quit))
and then I try to associate its result (which is a hash-map) into value of another map:
(assoc {} :1 actions)
but instead of expected result which should be:
{1: {"directions" :look, "look" :look ...
I receive
{:1 #object[fun_pro.core$actions 0x20a8027b "fun_pro.core$actions#20a8027b"]}
which is, as I understand reference to the action object.
What should I do to receive expected result? I tried also use of unquote-splicing but I'm not advanced enough to use macros yet and couldn't make it works.
EDIT1:
OK, It seem I found the solution. Instead of using (defn actions...) I should use (def actions...).
EDIT2:
To clarify why I use such a structure.
As I said in comment below, I will use this maps to compare it with the answer provided by user to find which command to use. For example if user type "show me directions", it will trigger function to display directions based on keyword "directions". The same result will be if user will ask "I look around the room" or "I examine room to find road", based on keywords "look" and "examine room".
It will be done by first splitting user input into set of strings and find if there is common word with keys from my map (turned into set). So input "show me directions" will be processed into set #{"show" "me" "directions"}. Then I will use clojure.set/intersection to find if there is common element with set of map keywords and trigger function accordingly to result (I have already coded algorithm for that).
Of course I'm open for any suggestions if there is better solution for it.
OK, It seem I found the solution on my own. Instead of using (defn actions...) I should use (def actions...).
This results of desired output.
Using Clojure, I'm pulling some data out of a SQLite DB. It will arrive in the form of a list of maps. Here is an abbreviated sample of what the data looks like.
(
{:department-id 1 :employee-firstname "Fred" :employee-lastname "Bloggs"}
{:department-id 1 :employee-firstname "Joe" :employee-lastname "Bloggs"}
{:department-id 2 :employee-firstname "John" :employee-lastname "Doe"}
...
)
I would like to reshape it into something like this:
(
{:department-id 1 :employees [{:employee-firstname "Joe" :employee-lastname "Bloggs"} {:employee-firstname "Fred" :employee-lastname "Bloggs"}]}
{:department-id 2 :employees [{:employee-firstname "John" :employee-lastname "Doe"}]
...
)
I know I could a write a function that dealt with the departments and then the employees and "glued" them back together to achieve the shape I want. In fact I did just that in the REPL.
But I've heard a bit about transducers recently and wondered was this an opportunity to use one.
If it is, what would the code look like?
I'll have a go, but like many of us, I'm still wrapping my head around this as well.
From my reading on transducers, it would seem the real benefit is in avoiding the need to create intermediate collections, thereby increasing efficiency. This means that to answer your question, you really need to look at what your code will be doing and how it is structure.
For example, if you had something like
(->>
(map ....)
(filter ..)
(map ..)
(map ..))
the functions are being run in sequence with new collections being created after each to feed into the next. However, with transducers, you would end up with something like
(->>
(map ...)
(map ..)
(filter ..)
(map ...))
where the functions being applied to the data are applied in a pipline fashion on each item from the original collection and you avoid the need to generate the intermediate collections.
In your case, I'm not sure it will help. This is partially because I don't know what other transformations you are applyinig, but mainly because what you are wanting requires a level of state tracking i.e. the grouping of the employee data. This is possible, but I believe it makes it a little harder.