I want change "aaa" or "aa..." to "." using Regex(re{2,})
Below is my code
var answer = "aaa"
var re = Regex("re{2,}a") // Regex("are{2,}")
answer = re.replace(answer,".")
println(answer)
Regex("re{2,}a") and Regex("are{2,}")
Both println aaa
How can I replace duplicated string using re{n,} ??
fun main(args: Array<String>) {
var tests = arrayOf("a","aa","aaa","aaaa")
val re = Regex("a(a+)")
tests.forEach {t->
val result = re.replace(t,".")
println(result)
}
}
output:
a
.
.
.
Generic regex to replace any duplicates (not only duplicate a symbols) is (?<symbol>.)\k<symbol>+
You may define an extension function for convenient usage:
private val duplicateRegex = "(?<symbol>.)\\k<symbol>+".toRegex()
fun String.replaceDuplicatesWith(replacement: String): String = replace(duplicateRegex, replacement)
Usage:
println("a".replaceDuplicatesWith(".")) //a
println("aaa".replaceDuplicatesWith(".")) //.
println("aa...".replaceDuplicatesWith(".")) //..
If you want duplicates to be iteratively replaced (like "aa..." -> ".." -> ".") you'll need an auxilary recursive method:
tailrec fun String.iterativelyReplaceDuplicatesWith(replacement: String): String {
val result = this.replaceDuplicatesWith(replacement)
return if (result == this) result else result.iterativelyReplaceDuplicatesWith(replacement)
}
Usage:
println("a".iterativelyReplaceDuplicatesWith(".")) //a
println("aaa".iterativelyReplaceDuplicatesWith(".")) //.
println("aa...".iterativelyReplaceDuplicatesWith(".")) //.
Related
I'm looking for a Kotlin way to do a dynamic values substitution into a string.
It is clear how to implement it, just want to check if there is something similar in standard library.
Could you help me to find a function which given template and data map returns a resulting string with all template keys replaced with their values?
fun format(template: String, data: Map<String, Any>): String { /* magic */ }
format("${a} ${b} ${a}", mapOf("a" to "Home", "b" to "Sweet)) // -> "Home Sweet Home"
fun format(template: String, data: Map<String, String>): String {
var retval = template
data.forEach { dataEntry ->
retval = retval.replace("\${" + dataEntry.key + "}", dataEntry.value)
}
return retval
}
// The $ signs in the template string need to be escaped to prevent
// string interpolation
format("\${a} \${b} \${a}", mapOf("a" to "Home", "b" to "Sweet"))
Not shorter than lukas.j's answer, just different (using Regex):
val regex = "\\\$\\{([a-z])}".toRegex()
fun format(template: String, data: Map<String, String>) =
regex.findAll(template).fold(template) { result, matchResult ->
val (match, key) = matchResult.groupValues
result.replace(match, data[key] ?: match)
}
I did not find any thing standard to solve the problem.
So here is a balanced (readability/performance/extensibility) solution also handling cases when some substitutions are undefined in dataMap.
makeString("\${a} # \${b} # \${c}", mapOf("a" to 123, "c" to "xyz")) // => "123 # ??? # xyz"
--
object Substitutions {
private val pattern = Pattern.compile("\\$\\{([^}]+)\\}")
fun makeString(
template: String,
dataMap: Map<String, Any?>,
undefinedStub: String = "???"
): String {
val replacer = createReplacer(dataMap, undefinedStub)
val messageParts = splitWithDelimiters(template, pattern, replacer)
return messageParts.joinToString("")
}
private fun createReplacer(dataMap: Map<String, Any?>, stub: String): (Matcher) -> String {
return { m ->
val key = m.group(1)
(dataMap[key] ?: stub).toString()
}
}
private fun splitWithDelimiters(
text: String,
pattern: Pattern,
matchTransform: (Matcher) -> String
): List<String> {
var lastMatch = 0
val items = mutableListOf<String>()
val m = pattern.matcher(text)
while (m.find()) {
items.add(text.substring(lastMatch, m.start()))
items.add(matchTransform(m))
lastMatch = m.end()
}
items.add(text.substring(lastMatch))
return items
}
}
New to Kotlin from Python. In Python, I can simply use the code below to pass each element of a List to a multiline function and return an iterator of the result.
countArr = list(map(countReps, arr))
In Kotlin, I found that I had to do the following. Am I missing something?
fun LetterCountI(str: String): String {
val arr = str.split(" ")
var transform:(String) -> Int = {countReps(it)}
val countArr = arr.map(transform)
val mxIndex:Int
var ans:String
if (countArr.max()!=1){
mxIndex = countArr.indexOf(countArr.max())
ans = arr[mxIndex]
} else {
ans = "-1"
}
return ans;
}
fun countReps(str: String): Int {
var m = mutableMapOf<Char, Int>()
var v:Int
for (c in str){
if (c in m.keys){
v = m[c]?:0
m.put(c,v+1)
} else {
m.put(c,1)
}
}
return m.values.max() ?: 0
}```
I'm having a bit of a hard time understanding your code, but one thing I can tell you is that you can replace
var transform:(String) -> Int = {countReps(it)}
val countArr = arr.map(transform)
with
val countArr = arr.map(::countReps)
In addition to the line you ask about, just about all of that code could be rewritten more concisely and idiomatically in Kotlin. For example:
fun String.wordWithMostRepeatedLetters()
= split(" ")
.associateWith{ it.maxRepeatedLetters() }
.filter{ it.value > 1 }
.maxByOrNull{ it.value }?.key ?: "-1"
fun String.maxRepeatedLetters()
= groupBy{ it }.map{ it.value.size }.maxOrNull() ?: 0
I've renamed the functions to try to explain what they give; replaced the countArr list with a map from each word to its count, so that you don't need to re-scan it to find the word resulting; and changed both functions to take a String receiver instead of a parameter. Then, because each variable was only used once, I removed them and made it all in-line, using an expression body for each function.
Some of those things don't always improve clarity, of course, especially for long functions — but I hope it demonstrates how concise Kotlin can be. (Hopefully without sacrificing maintainability. Which version would be easier to read? Which would be more likely to harbour subtle bugs?)
It's still not clear what the hard-coded "-1" return value indicates, though… If no word has any repeated letters, a null return would be more idiomatic. (Or it would be simpler just to return the first word, removing the filter() call, and returning null only if the string is blank.)
I am trying to return List<List<Map<String, String>>> from a function in kotlin. I'm new to kotlin.
Edit1
Here's how I am attempting to to this
val a = mutableListOf(mutableListOf(mutableMapOf<String, String>()))
The problem with the above variable is, I am unable to figure out how to insert data into this variable. I tried with this:
val a = mutableListOf(mutableListOf(mutableMapOf<String, String>()))
val b = mutableListOf(mutableMapOf<String, String>())
val c = mutableMapOf<String, String>()
c.put("c", "n")
b.add(c)
a.add(b)
This is giving me:
[[{}], [{}, {c=n}]]
What I want is [[{c=n}]]
Can someone tell me how I can insert data into it?
The end goal I am trying to achieve is to store data in the form of List<List<Map<String, String>>>
EDIT 2
The function for which I am trying to write this dat structure:
fun processReport(file: Scanner): MutableList<List<Map<String, String>>> {
val result = mutableListOf<List<Map<String, String>>>()
val columnNames = file.nextLine().split(",")
while (file.hasNext()) {
val record = mutableListOf<Map<String, String>>()
val rowValues = file.nextLine()
.replace(",(?=[^\"]*\"[^\"]*(?:\"[^\"]*\"[^\"]*)*$)".toRegex(), "")
.split(",")
for (i in rowValues.indices) {
record.add(mapOf(columnNames[i] to rowValues[i]))
print(columnNames[i] + " : " + rowValues[i] + " ")
}
result.add(record)
}
return result
}
You don't need to use mutable data structures. You can define it like this:
fun main() {
val a = listOf(listOf(mapOf("c" to "n")))
println(a)
}
Output:
[[{c=n}]]
If you wanted to use mutable data structures and add the data later, you could do it like this:
fun main() {
val map = mutableMapOf<String, String>()
val innerList = mutableListOf<Map<String, String>>()
val outerList = mutableListOf<List<Map<String, String>>>()
map["c"] = "n"
innerList.add(map)
outerList.add(innerList)
println(outerList)
}
The output is the same, although the lists and maps are mutable.
In response to the 2nd edit. Ah, you're parsing a CSV. You shouldn't try to do that yourself, but you should use a library. Here's an example using Apache Commons CSV
fun processReport(file: File): List<List<Map<String, String>>> {
val parser = CSVParser.parse(file, Charset.defaultCharset(), CSVFormat.DEFAULT.withHeader())
return parser.records.map {
it.toMap().entries.map { (k, v) -> mapOf(k to v) }
}
}
For the following CSV:
foo,bar,baz
a,b,c
1,2,3
It produces:
[[{foo=a}, {bar=b}, {baz=c}], [{foo=1}, {bar=2}, {baz=3}]]
Note that you can simplify it further if you're happy returning a list of maps:
fun processReport(file: File): List<Map<String, String>> {
val parser = CSVParser.parse(file, Charset.defaultCharset(), CSVFormat.DEFAULT.withHeader())
return parser.records.map { it.toMap() }
}
Output:
[{foo=a, bar=b, baz=c}, {foo=1, bar=2, baz=3}]
I'm using Charset.defaultCharset() here, but you should change it to whatever character set the CSV is in.
i want get text from a file by using regEx and want save the file with a new name (using the results of the regEx-Find).
My Problem is that i cant get/return the correct genearated (in this example xyz maur) out of the function readFileLineByLineUsingForEachLine(fileName: String) the new newFileName which was generated (sucessfully as expected) in the function.
Line 1 of Source:
start {"Name":"xyz","Civ":"maur","Team":0}
My Prototype:
fun main() {
val f = "./commands.txt";
var newFileName = readFileLineByLineUsingForEachLine(f)
print(newFileName.)
val source = Paths.get(f)
val target = Paths.get("/home/x/snap/0ad/199/.local/share/0ad/replays/0.0.24/2021-03-14_0016/" + newFileName)
// try {
// val move = Files.move(
// source,
// target
// )
// } catch (e: IOException) {
// e.printStackTrace()
// }
};
fun readFileLineByLineUsingForEachLine(fileName: String) // https://www.baeldung.com/kotlin/read-file
= File(fileName).forEachLine lit#{
// "Name":"Cleisthenes"
val regexString = """
"Name":(?<Name>"\w+").*?"Civ":(?<Civ>"\w+").*?"Team":0
""".trim()
var regex = Regex(regexString)
var matched = regex.find(it)?.groupValues
val Name = matched?.get(1)
val Civ = matched?.get(2)
if (Name != null)
println(Name)
if (Civ != null)
println(Civ)
val newFileName = "$Name $Civ"
return#lit
}
Because you want to stop processing as soon as you find a match, I don't think forEachLine is the best choice. Instead you can use useLines, and combine it with first to stop processing once you get a match:
val regex = Regex(""""Name":(?<Name>"\w+").*?"Civ":(?<Civ>"\w+").*?"Team":0""")
fun readFileLineByLineUsingForEachLine(fileName: String) =
File(fileName).useLines { lines ->
val (name, civ) = lines
.map { regex.find(it) }
.filterNotNull()
.first()
.destructured
"$name $civ"
}
For the example you provided, this returns the string "xyz" "maur".
that's just a very little modification of the correct, helpful answer from Adam here https://stackoverflow.com/a/66654710/2891692
fun readFileLineByLineUsingForEachLine2(fileName: String) =
File(fileName).useLines { lines ->
val (name, civ) = lines
.map {
val regexString = """
"Name":(?<Name>"\w+").*?"Civ":(?<Civ>"\w+").*?"Team":0
""".trim()
var regex = Regex(regexString)
regex.find(it)
}
.filterNotNull()
.first()
.destructured
"$name $civ"
}
How to replace many parts of a string with something else in Kotlin using .replace()
For example, we can do it only by replacing one word
fun main(args: Array<String>) {
var w_text = "welcome his name is John"
println("${w_text.replace("his","here")}")
}
and the result will be " welcome here name is John " .
finally we need the result be " welcome here name is alles "
by replacing his to here and john to alles using .replace()
You can do it using multiple consecutive calls to replace():
w_text.replace("his", "here").replace("john", "alles")
You could write an extension that overloads String::replace:
fun String.replace(vararg replacements: Pair<String, String>): String {
var result = this
replacements.forEach { (l, r) -> result = result.replace(l, r) }
return result
}
fun main(args: Array<String>) {
val sentence = "welcome his name is John"
sentence.replace("his" to "here", "John" to "alles")
}
If you have many of those replacement rules, then create a mapping of them and call the replace method in a loop:
val map = mapOf("his" to "here", "john" to "alles", ...)
val sentence = "welcome his name is John"
var result = sentence
map.forEach { t, u -> result = result.replace(t, u) }
println(result)
For the ones interested in replacing a map of values in a text:
private fun replaceText(text: String, keys: Map<String, String>): String =
val replaced = map.entries.fold(text) { acc, (key, value) -> acc.replace(key, value) }
Here is a one liner:
fun String.replace(vararg pairs: Pair<String, String>): String =
pairs.fold(this) { acc, (old, new) -> acc.replace(old, new, ignoreCase = true) }
Test:
#Test fun rep() {
val input = "welcome his name is John"
val output = input.replace("his" to "her", "john" to "alles")
println(output)
output shouldBeEqualTo "welcome her name is alles"
}
Similar to other responses but using Kotlin extension and overloading String::replace to accept a map of oldValue to newValue.
fun String.replace(mapping: Map<String, String>): String {
var str = this
mapping.forEach { str = str.replace(it.key, it.value) }
return str
}
Usage:
val mapping = mapOf("his" to "here", "John" to "alles")
"his dad is John".replace(mapping) // here dad is alles
The issue with just using replace without any regex is:
Let's say I want to replace the occurrence of "here" with "there" inside the string "Where is my bag? Your bag is here." As you can imagine the result will be "Wthere is my bag? Your bag is there." which will not be correct. The solution is to use a regex like given below.
var str = "Where is my bag? Your bag is here."
val replacements = setOf("\\bhere\\b" to "there",
"\\bjohn\\b" to "alles")
replacements.forEach {
str = str.replace(Regex(it.first), it.second)
}