Add alternate receive bbe

examples/alternate-receive/alternate_receive.bal

@@ -0,0 +1,47 @@
+import ballerina/io;
+import ballerina/lang.runtime;
+
+public function main() {
+ worker w1 {
+ 2 -> w3;
+ }
+
+ worker w2 {
+ runtime:sleep(2);
+ 3 -> w3;
+ }
+
+ worker w3 returns int {
+ // The value of the variable `result` is set as soon as the values from either
+ // worker `w1` or `w2` is received.
+ int result = <- w1 | w2;
+ return result;
+ }
+
+ worker w4 returns error? {
+ int value = 10;
+ if value == 10 {
+ return error("Error in worker 1");
+ }
+ value -> w6;
+ }
+
+ worker w5 {
+ runtime:sleep(2);
+ 3 -> w6;
+ }
+
+ worker w6 returns int|error? {
+ // Alternate receive action waits until a message that is not an error is received 
+ // when error is not an expected static type. Since `w4` returns an error it 
+ // waits further and sets the value that is received from `w5`.
+ int a = check <- w4 | w5;
+ return a;
+ }
+
+ int valueW3 = wait w3;
+ io:println(valueW3);
+
+ int|error? valueW6 = wait w6;
+ io:println(valueW6);
+}

examples/alternate-receive/alternate_receive.md

@@ -0,0 +1,7 @@
+# Alternate receive
+
+The alternate receive action can be used to receive values from several workers.
+
+::: code alternate_receive.bal :::
+
+::: out alternate_receive.out :::

examples/alternate-receive/alternate_receive.metatags

@@ -0,0 +1,2 @@
+description: This BBE demonstrates the alternate receive action
+keywords: ballerina, ballerina by example, bbe, worker, alternate receive

examples/alternate-receive/alternate_receive.out

@@ -0,0 +1,3 @@
+$ bal run alternate_receive.bal
+2
+3

examples/index.json

@@ -1419,6 +1419,13 @@
  "disableVerificationReason": "Includes varying output",
  "isLearnByExample": true
  },
+ {
+ "name": "Alternate receive",
+ "url": "alternate-receive",
+ "verifyBuild": true,
+ "verifyOutput": true,
+ "isLearnByExample": true
+ },
  {
  "name": "Multiple wait",
  "url": "multiple-wait",