https://github.com/pgreze/kounter
📚 Counting easily with Kotlin, and more.
https://github.com/pgreze/kounter
counter default kotlin map
Last synced: 3 months ago
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📚 Counting easily with Kotlin, and more.
- Host: GitHub
- URL: https://github.com/pgreze/kounter
- Owner: pgreze
- License: apache-2.0
- Created: 2020-01-05T12:25:29.000Z (over 5 years ago)
- Default Branch: main
- Last Pushed: 2022-08-10T12:46:51.000Z (almost 3 years ago)
- Last Synced: 2025-01-12T05:28:42.932Z (4 months ago)
- Topics: counter, default, kotlin, map
- Language: Kotlin
- Homepage: https://kounter.netlify.app
- Size: 120 KB
- Stars: 2
- Watchers: 3
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Kounter [](https://opensource.org/licenses/Apache-2.0)  
Choose the easy-to-use **Counter** or the fully flexible **MapWithDefault**.
## Installation [](https://search.maven.org/artifact/com.github.pgreze/kounter)
```kotlin
dependencies {
// Check the 🔝 maven central badge 🔝 for the latest $version
implementation("com.github.pgreze:kounter:$version")
}
repositories {
jcenter()
}
```
## Usage [](https://kounter.netlify.app/)
### Counter / MutableCounter
A specialization of the Map class allowing to count objects.
This is similar to [Guava Multiset](https://guava.dev/releases/19.0/api/docs/com/google/common/collect/Multiset.html)
or [Python Counter](https://docs.python.org/3.8/library/collections.html#collections.Counter),
inspired by [older references](https://github.com/python/cpython/blob/ec007cb43faf5f33d06efbc28152c7fdcb2edb9c/Lib/collections/__init__.py#L516)
like [Smalltalk Bag class](http://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html).
Usage:
```kotlin
val lints = mutableCounterOf("warnings" to 20)
lints["warnings"] += 3
lints["errors"] += 1
println(lints) // {warnings=23, errors=1}
```
Helpers:
```kotlin
counterOf("aabbbcc") // {a=2, b=3, c=2}
counterOf(arrayOf('a', 'b', 'b', 'c')) // {a=1, b=2, c=1}
counterOf(listOf('a', 'a', 'b', 'c')) // {a=2, b=1, c=1}
counterOf(setOf('a', 'b', 'c')) // {a=1, b=1, c=1}
```
To perform mathematical operations on counters, use following methods:
```kotlin
val c1 = counterOf("ab")
val c2 = counterOf("ccd")
c1.plusAll(c2) // {a=2, b=3, c=2}
val chars = mutableCounterOf("ab")
chars.addAll(counterOf("ccd")) // {a=2, b=3, c=2}
```
### MapWithDefault / MutableMapWithDefault
**Counter / MutableCounter** are internally using these classes.
There are also an alternative of
[withDefault](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/with-default.html)
which is a memory efficient way to specify a default value for a Map but sadly,
not reflecting this change in its signature.
It's forcing users to use an unnatural
[getValue](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/get-value.html) extension method,
which is not the [most intuitive way of using a Map](https://discuss.kotlinlang.org/t/map-withdefault-not-defaulting/7691).
Proposed alternative is slightly changing the original Map interface:
```kotlin
interface MapWithDefault : Map {
override fun get(key: K): V
}
```
Allowing to unlock a better syntax:
```kotlin
val money = mutableMapOf("Alice" to 5)
.setDefault { 0 }
money["Alice"] += 10
money["Bob"] += 3
println(money) // {Alice=15, Bob=3}
```
Which is shining when used with Set/List/Map:
```kotlin
val sets = mutableMultiSetWithDefaultOf()
// Alias for mutableMapOf>().setDefault { setOf() }
sets += "Alice" to setOf("f1.txt")
sets["Bob"] += setOf("f2.md")
println(sets) // {"A0"= setOf("f1.txt"), "A1"= setOf("f2.md")}
```
Following helpers are available for common native collections:
| | + setDefault | Mutable + setDefault |
|------|------------------------|-------------------------------|
| List | multiListWithDefaultOf | mutableMultiListWithDefaultOf |
| Set | multiSetWithDefaultOf | mutableMultiSetWithDefaultOf |
| Map | multiMapWithDefaultOf | mutableMultiMapWithDefaultOf |
Alternative: [Guava collection package](https://guava.dev/releases/19.0/api/docs/com/google/common/collect/package-summary.html)
including [Multimap](https://guava.dev/releases/19.0/api/docs/com/google/common/collect/Multimap.html)
implemented by [ListMultimap](https://guava.dev/releases/19.0/api/docs/com/google/common/collect/ListMultimap.html)
or [SetMultimap](https://guava.dev/releases/19.0/api/docs/com/google/common/collect/SetMultimap.html).