More Kotlin

Author: rtoal

cpp/scope_operator.cpp

@@ -0,0 +1,18 @@
+#include <cassert>
+int x = 1;
+
+namespace N {
+  int x = 2;
+};
+
+struct C {
+  int x = 3;
+  void f() {
+    int x = 4;
+    assert(::x == 1 && N::x == 2 && C::x == 3 && x == 4);
+  }
+};
+
+int main() {
+  C().f();
+}

js/strings.js

@@ -1,6 +1,6 @@
 import assert from "assert/strict"
 
-const s = "\u{1f363}\u{2669}"
-assert(s.length === 3) // this is honestly rather silly
+const s = "\u{1f363}\u{2669}" // SUSHI, QUARTER NOTE
+assert(s.length === 3) // based on internal storage units
 assert(Array.from(s).length === 2) // ok, 2 code points
 assert(Buffer.from(s, "utf8").length === 7) // ok, 7 bytes utf-8

kotlin/binding.kts

@@ -0,0 +1,12 @@
+fun display(displayer: () -> Unit) {
+  var name = "new"
+  displayer()     // what if "name" was free in this function?
+}
+
+fun main() {
+  var name = "old"
+  fun printName() { print(name) }
+  display(::printName)
+}
+
+main()

kotlin/closures.kts

@@ -0,0 +1,13 @@
+@file:DependsOn("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.1")
+import kotlinx.coroutines.*
+
+runBlocking {
+    repeat(5) {
+        launch {
+            println("Coroutine $it running on ${Thread.currentThread().name}.")
+            delay((1000L..5000L).random())
+            println("Coroutine $it finished on ${Thread.currentThread().name}.")
+        }
+    }
+    println("All coroutines launched")
+}

kotlin/coroutines.main.kts

@@ -0,0 +1,44 @@
+@file:DependsOn(
+    "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.1",
+    "com.squareup.okhttp3:okhttp:4.11.0",
+    "org.json:json:20230618",
+)
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import okhttp3.Response
+import org.json.JSONObject
+
+val baseUrl = "https://pokeapi.co/api/v2/pokemon/"
+val pokemonNames = listOf("ditto", "pikachu", "mew", "weedle", "eevee")
+
+data class PokeInfo(val name: String, val height: Int, val weight: Int)
+
+suspend fun fetchPokemon(name: String) {
+    println("Fetching $name on ${Thread.currentThread().name}")
+    val request = Request.Builder().url("$baseUrl$name").build()
+    val response = OkHttpClient().newCall(request).execute()
+    if (!response.isSuccessful) {
+        println("Cannot fetch $name: HTTP ${response.code}")
+        return
+    }
+    val jsonObject = JSONObject(response.body?.string() ?: return)
+    println(PokeInfo(
+        jsonObject.getString("name"),
+        jsonObject.getInt("height"),
+        jsonObject.getInt("weight")))
+}
+
+runBlocking {
+    for (name in pokemonNames) {
+        launch(Dispatchers.IO) {
+            fetchPokemon(name)
+        }
+    }
+    println("The fetches are underway")
+}
+println("The fetches are done")
+

kotlin/poke_api.main.kts

@@ -2,7 +2,6 @@
 kotlin -J-ea animals.kts && \
 kotlin -J-ea binary_tree.kts && \
 kotlin circle.kts && \
-kotlin closures.kts && \
 kotlin codepoints.kts && \
 kotlin collections.kts && \
 kotlin companions.kts && \