string = "bonjor hello how are you you you";
Can anybody provide me with the code to count how many times the word you is within the string? I just cant get it.
Greatly appreciate any help!
hey check these and let me know if still have any doubt
(def data "bonjor hello how are you you you")
(count (re-seq #"you" data))
check documentation of
re-seq and count for detail.
detailed documentation available here:
Grimoire and
clojure docs
Related
I am a beginner in clojure. I am trying to solve this simple problem on codechef using clojure. Below is my clojure code but this code is taking too long to run and gives TimeoutException. Can someone please help me to optimize this code and make it run faster.
(defn checkCase [str]
(let [len (count str)]
(and (> len 1) (re-matches #"[A-Z]+" str))))
(println (count (filter checkCase (.split (read-line) " "))))
Note: My program is not getting timedout due to input error. On codechef input is handled automatically (probably through input redirection. Please read the question for more details)
Thank you!
Most text finding exercises are exercizes in regexps, this one no different. It's usually pretty hard to find a more efficient way in whatever programming language that will outpace good regexp implementations.
In this case re-seq, look around regexps, repetition limiting and the multiline regexp flag (?m) are your friends
(defn find-acronyms
[s]
(re-seq #"(?m)(?<=\W|^)[A-Z]+(?=\W|$)" s))
(find-acronyms "I like coding and will participate in IOI Then there is ICPC")
=> ("IOI" "ICPC")
Let's dissect the regex:
(?m) The multiline flag: lets you match your regex over multiple lines, so no need to split into multiple strings
(?<=\W|^) The match should follow a non-word character or the beginning of the (multiline) string
[A-Z]{2,} Match concurrent capital letters, a minimum of 2
(?=\W|$) The match should be followed by a non-word character or the end of the (multiline) string
I can only guess that wherever you run this snippet of code, it doesn't feed anything to your read-line invocation. Or maybe it does, but doesn't send a newline as the last thing. So it hangs waiting.
(defn checkCase [str]
(let [len (count str)]
(and (> len 1) (re-matches #"[A-Z]+" str))))
(defn answer [str]
(println (count (filter checkCase (.split str " ")))))
So at the REPL:
=> (answer "GGG fff TTT")
;-> 2
;-> nil
The answer is being printed to the screen. But probably best to have your function return the answer rather than print it out:
(defn answer [str]
(count (filter checkCase (.split str " "))))
All I have done is replaced your (read-line) with an argument. (read-line) is expecting input from stdin and waiting for it forever - or until a timeout happens in your case.
I am not sure if this is the slow part of your code, but if it is your could try to split up the execution and safe gard the very slow regexp part by executing it when it is necessary. I think the current version with AND already does that. If it does not you can try to do something else, like this:
(defn checkCase [^String str]
(cond
(< (.length str) 2)
false
(re-matches #"[A-Z]+" str)
true
:else
false))
maybe you could try using re-seq instead of spltting the string and checking every item? So you will lose the filter, .split, and additional function call. Something like this:
(println (count (re-seq #"\b[A-Z]{2,}?\b" (read-line))))
You need to submit a Java program. You can test it on the command line before you submit it. You can but don't need to use redirection symbols (<,>). Just type the input and see that every time you do it returns the count after you have typed enter.
You will need aot compilation (Ahead Of Time, which means that .class files are included) and a main that is exported. Only then will it become a Java program.
Actually when they ask for a Java program they probably mean a .class file. You can run a .class file with the java program (which I imagine is what their test-runner does). Put it in a shell or batch file when testing, but just submit the .class file.
I am trying to make a very simple Nim game that probably isn't even considered a proper implementation of Nim, but I am only starting Clojure. Not sure why this subtraction on line four doesn't work...
1. (def nimBoard 10)
2. (println "There are" nimBoard "objects left")
3. (def in (read-line))
4. (- nimBoard in)
I can't seem to come up with a solid algorithm for asking the user if they want to remove one or two "objects" from the board until it is empty. I am coming from Java, but loops in this language just confuse me a lot. I know what I am trying to make isn't exactly the Game of Nim, but it is for practice.
I would appreciate any help:)
Since in is a string you read from standard in, you need to convert in to a number first before the subtraction. Try this:
(defn parse-int [s]
(Integer. (re-find #"\d+" s )))
(- nimBoard (parse-int in))
I've been trying to get a simple reg-ex working in Clojure to test a string for some SQL reserved words (select, from, where etc.) but just can't get it to work:
(defn areserved? [c]
(re-find #"select|from|where|order by|group by" c))
(I split a string by spaces then go over all the words)
Help would be greatly appreciated,
Thanks!
EDIT: My first goal (after only reading some examples and basic Clojure materials) is to parse a string and return for each part of it (i.e. words) what "job" they have in the statement (a reserved word, a string etc.).
What I have so far:
(use '[clojure.string :only (join split)])
(defn isdigit? [c]
(re-find #"[0-9]" c))
(defn isletter? [c]
(re-find #"[a-zA-Z]" c))
(defn issymbol? [c]
(re-find #"[\(\)\[\]!\.+-><=\?*]" c))
(defn isstring? [c]
(re-find #"[\"']" c))
(defn areserved? [c]
(if (re-find #"select|from|where|order by|group by" c)
true
false))
(defn what-is [token]
(let [c (subs token 0 1)]
(cond
(isletter? c) :word
(areserved? c) :reserved
(isdigit? c) :number
(issymbol? c) :symbol
(isstring? c) :string)))
(defn checkr [token]
{:token token
:type (what-is token)})
(defn goparse [sql-str]
(map checkr (.split sql-str " ")))
Thanks for all the help guys! it's great to see so much support for such a relatively new language (at least for me :) )
I'm not entirely sure what you want exactly, but here's a couple of variations to coerce your first regex match to a boolean:
(defn areserved? [c]
(string?
(re-find #"select|from|where|order by|group by"c)))
(defn areserved? [c]
(if (re-find #"select|from|where|order by|group by"c)
true
false))
UPDATE in response to question edit:
Thanks for posting more code. Unfortunately there are a number of issues here that we could
try to address by patching your existing code in a simplistic and naïve fashion, but it will
only get you so far, before you hit the next problem with this single iteration approach.
#alex is correct, that your areserved? method will fail to match order by if you have already
split your string by white space. That said, a simple fix is to treat order and by as separate keywords (which they are, even though they always appear together).
The next issue is that the areserved? function will match keywords in a string, but you are dispatching it against a character in the what-is function. You nearly always get a match in your cond for isletter?, so you will everything is marked as a 'word'.
All in all, it looks like you are trying to do too much work in a single application of map.
I'm not sure if you are just doing this for fun to play with Clojure (which is admirable - keep going!), in which case, maybe it doesn't matter if you press on with this simple parsing approach... you'll definitely learn something; but if you would like to take it further and parse SQL more successfully, then I would suggest that you may find it helpful to to read a little on Lexing, Parsing and building Abstract Syntax Trees (AST).
Brian Carper has written about using the Java parser generator "ANTLR" from Clojure - it's a few years old, but might be worth looking at.
You also might be able to get some transferrable ideas from this chapter from the F# programming book on lexing and parsing SQL.
I have been struggling to find an answer or develop a solution. I am trying to figure out how to make code that makes code in Clojure. For my first feat, I want a function that will print to stdout the name of the symbol and its value, useful for debugging. Example:
(def mysymbol 5)
(debugging-function mysymbol)
mysymbol: 5
Does that make sense? Thanks for your help.
Post Discussion Update
Here is the answer from #amalloy:
(defmacro ?
"A useful debugging tool when you can't figure out what's going on:
wrap a form with ?, and the form will be printed alongside
its result. The result will still be passed along."
[val]
`(let [x# ~val]
(prn '~val '~'is x#)
x#))
So:
(? myvariable)
You can see a simple version of this that I wrote on github. The main point is that you can't do this with a function, but with a macro it's simple enough - you just have to get your quoting and unquoting right.
Given a string, I want to replace all links within it with the link's description. For example, given
this is a [[http://link][description]]
I would like to return
this is a description
I used re-builder to construct this regexp for a link:
\\[\\[[^\\[]+\\]\\[[^\\[]+\\]\\]
This is my function:
(defun flatten-string-with-links (string)
(replace-regexp-in-string "\\[\\[[^\\[]+\\]\\[[^\\[]+\\]\\]"
(lambda(s) (nth 2 (split-string s "[\]\[]+"))) string))
Instead of replacing the entire regexp sequence, it only replaces the trailing "]]". This is what it produces:
this is a [[http://link][descriptiondescription
I don't understand what's going wrong. Any help would be much appreciated.
UPDATE: I've improved the regex for the link. It's irrelevant to the question but if someone's gonna copy it they may as well get the better version.
Your problem is that split-string is clobbering the match data, which
replace-regexp-in-string is relying on being unchanged, since it is going to
go use that match data to decide which sections of the string to cut out. This
is arguably a doc bug in that replace-regexp-in-string does not mention that
your replacement function must preserve the match data.
You can work around by using save-match-data, which is a macro provided for
exactly this purpose:
(defun flatten-string-with-links (string)
(replace-regexp-in-string "\\[\\[[a-zA-Z:%#/\.]+\\]\\[[a-zA-Z:%#/\.]+\\]\\]"
(lambda (s) (save-match-data
(nth 2 (split-string s "[\]\[]+")))) string))