Add Rosetta Code 'Averages/RArithmetic mean' task (from Daniel Shindler)

rosettacode/Averages-Arithmetic mean.stdout

@@ -0,0 +1 @@
+20

rosettacode/Averages-Arithmetic mean.ursa

@@ -0,0 +1,8 @@
+let mean = fn(l) {
+  var tot = 0
+  for i in l.iter() {
+    tot := tot + i
+  }
+  return tot / l.len()
+}
+print(mean([10, 30, 50, 5, 5]))

src/ursa/examples.test.ts

@@ -57,6 +57,7 @@ import {
   // Rosetta code examples
   ['Accumulator factory', 'rosettacode/Accumulator factory'],
   ['Ackermann function', 'rosettacode/Ackermann function'],
+  ['Averages/Arithmetic mean', 'rosettacode/Averages-Arithmetic mean'],
   ['Averages/Root mean square', 'rosettacode/Averages-Root mean square'],
   // This program has an unbound variable
   // ['Conditional structures', 'rosettacode/Conditional structures'],