Apparently I can't read-string some strings, like
user> (read-string "\" \\ABC \"")
RuntimeException Unsupported escape character: \A clojure.lang.Util.runtimeException (Util.java:219)
user>
Is there a way around that?
Thanks!
I assume that you want to end up with a string that when you print its "\ABC", so:
user=> (println "\\ABC")
\ABC
nil
As you see, the reader needs two "\". As read-string expects the string to be a valid Clojure expression and from your example you are trying to read a string that contains a string, you need to escape both the " (as you are doing) and the two \ :
user=> (def s (read-string "\" \\\\AB\""))
#'user/s
user=> (class s)
java.lang.String
user=> (println s)
\AB
nil
user=> s
" \\AB"
Related
I want to replace a character in a string using index. How to do that? Or is there any other way of accessing it?
Like almost everything commonly used in Clojure, strings are immutable, so you need to create a new string with the new character in place of the old at the desired location:
(defn replace-at [s idx replacement]
(str (subs s 0 idx) replacement (subs s (inc idx))))
> (replace-at "012345" 2 "x")
01x345
Strings are immutable, but StringBuilderss are not, so you could leverage that:
(defn set-char-at [^String s idx ch]
(str (doto (StringBuilder. s) (.setCharAt idx ch))))
(set-char-at "foobar" 2 \x) ;;=> "foxbar"
I have a string "Hello" and I want to replace the characters between the two indexes with another string, say "Foo". E.g.
(defn new-replace [orig-str start-index end-index new-string] ...)
(= "Foollo" (new-replace "Hello" 0 2 "Foo")) => true
(= "Foolo" (new-replace "Hello" 0 3 "Foo")) => true
Any suggestions? Cheers
Here's one way:
(defn new-replace [orig-str start-index end-index new-string]
(str (apply str (take start-index orig-str))
new-string
(apply str (drop end-index orig-str))))
Stringbuffer already provieds a replace function:
(defn new-replace [orig-str start-index end-index new-string]
(str (.replace (StringBuffer. orig-str) start-index end-index new-string)))
Input: "Michael" "Julia" "Joe" "Sam"
Output: Hi, Michael, Julia, Joe, and Sam. (pay attention to the commas and the word "and")
Input: nil
Output: Hi, world.
Here is my first attempt:
(defn say-hi [& name]
(print "Hi," name))
user> (say-hi "Michael")
Hi, (Michael)
nil
user> (say-hi "Michael" "Julia")
Hi, (Michael Julia)
nil
Question:
How to implement default: (no input, say "Hi World!")
How to get rid of the parents around names in output?
How to implement the commas separation and add the conjunction word "and"?
First off, Clojure supports multi-arity functions, so you could do something like this to achieve default behaviour:
(defn say-hi
([] (say-hi "World"))
([& names] ...))
Then, what you want is to take a seq and join all the strings it contains together, using ", " in between. The clojure.string namespaces contains lots of string manipulation functions, one of them being clojure.string/join:
(require '[clojure.string :as string])
(string/join ", " ["Michael", "Julia"])
;; => "Michael, Julia"
But the last element of the seq should be concatenated using " and " as a separator, so you'll end up with something like this:
(require '[clojure.string :as string])
(defn say-hi
([] (say-hi "World"))
([& names]
(if (next names)
(format "Hi, %s, and %s!"
(string/join ", " (butlast names))
(last names))
(format "Hi, %s!" (first names)))))
Note that you have to differentiate between the single- and multi-name cases and (next names) basically checks whether the seq contains more than one element. (You could achieve the same by adding another arity to the function.)
(say-hi)
;; => "Hi, World!"
(say-hi "Michael")
;; => "Hi, Michael!"
(say-hi "Michael" "Julia" "Joe" "Sam")
;; => "Hi, Michael, Julia, Joe, and Sam!"
You can use clojure.string/join:
(use '[clojure.string :only [join]])
(defn sentencify [& elems]
(->>
[(join ", " (butlast elems)) (last elems)]
(remove empty?)
(join " and ")))
(defn say-hi [& name]
(print "Hi," (if name
(sentencify name)
"World!")))
A concise solution:
(defn say-hi [& names]
(let [names (case (count names)
0 ["world"]
1 names
(concat (butlast names) (list (str "and " (last names)))))]
(->> names, (cons "Hi"), (interpose ", "), (apply str))))
(say-hi)
;"Hi, world"
(say-hi "Michael")
;"Hi, Michael"
(say-hi "Michael" "Julia" "Joe" "Sam")
;"Hi, Michael, Julia, Joe, and Sam"
For long lists of names, you would want to eschew count, last, and butlast, maybe by pouring names into a vector first.
To print (as the question does) rather than return the formatted string, append print to the final form:
(->> names, (cons "Hi"), (interpose ", "), (apply str), print)
I can read some data in like this in the repl. For a real program I plan to assign in a let special form.
(def x1 (line-seq (BufferedReader. (StringReader. x1))))
If I enter 5 5, x1 is bound to ("5 5")
I would like to convert this list of one element into a list of two integers. How can I do that? I have been playing around with parsing the string on whitespace, but am having trouble performing the conversion to integer.
Does this help? In Clojure 1.3.0:
(use ['clojure.string :only '(split)])
(defn str-to-ints
[string]
(map #(Integer/parseInt %)
(split string #" ")))
(str-to-ints "5 4")
; => (5 4)
(apply str-to-ints '("5 4"))
; => (5 4)
In case the Clojure version you're using doesn't have clojure.string namespace you can skip the use command and define the function in a following way.
(defn str-to-ints
[string]
(map #(Integer/parseInt %)
(.split #" " string)))
You can get rid of regular expressions by using (.split string " ") in the last line.
Works for all numbers and returns nil in the case it isn't a number (so you can filter out nils in the resulting seq)
(require '[clojure.string :as string])
(defn parse-number
"Reads a number from a string. Returns nil if not a number."
[s]
(if (re-find #"^-?\d+\.?\d*$" s)
(read-string s)))
E.g.
(map parse-number (string/split "1 2 3 78 90 -12 0.078" #"\s+"))
; => (1 2 3 78 90 -12 0.078)
The string can be wrapped with brackets and after that evaluated as clojure list with read-string function:
(def f #(read-string (str "(" % ")")))
(f "5 4")
; => (5 4)
In my application I need to convert clojure keyword eg. :var_name into a string "var_name". Any ideas how that could be done?
user=> (doc name)
-------------------------
clojure.core/name
([x])
Returns the name String of a string, symbol or keyword.
nil
user=> (name :var_name)
"var_name"
Actually, it's just as easy to get the namespace portion of a keyword:
(name :foo/bar) => "bar"
(namespace :foo/bar) => "foo"
Note that namespaces with multiple segments are separated with a '.', not a '/'
(namespace :foo/bar/baz) => throws exception: Invalid token: :foo/bar/baz
(namespace :foo.bar/baz) => "foo.bar"
And this also works with namespace qualified keywords:
;; assuming in the namespace foo.bar
(namespace ::baz) => "foo.bar"
(name ::baz) => "baz"
Note that kotarak's answer won't return the namespace part of keyword, just the name part - so :
(name :foo/bar)
>"bar"
Using his other comment gives what you asked for :
(subs (str :foo/bar) 1)
>"foo/bar"
It's not a tedious task to convert any data type into a string, Here is an example by using str.
(defn ConvertVectorToString []
(let [vector [1 2 3 4]]
(def toString (str vector)))
(println toString)
(println (type toString)
(let [KeyWordExample (keyword 10)]
(def ConvertKeywordToString (str KeyWordExample)))
(println ConvertKeywordToString)
(println (type ConvertKeywordToString))
(ConvertVectorToString) ;;Calling ConvertVectorToString Function
Output will be:
1234
java.lang.string
10
java.lang.string
This will also give you a string from a keyword:
(str (name :baz)) -> "baz"
(str (name ::baz)) -> "baz"