While loops.

examples/while_test.fun

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+#!/usr/bin/env fun
+
+// While loops feature test: simple loops, nested with if/else, and functions
+
+print("=== while test start ===")
+
+// Simple counter 0..4
+number i = 0
+while (i < 5)
+  print(i)        // expect 0,1,2,3,4
+  i = i + 1
+
+// Nested while with if/else
+number a = 3
+while (a > 0)
+  if (a == 2)
+    print(99)     // special case when a == 2
+  else
+    print(a)
+  a = a - 1       // expect: 3, 99, 1
+
+// While with false condition: body should not run
+while (0)
+  print(123)
+
+// Function using while
+fun countdown(n)
+  while (n > 0)
+    print(n)
+    n = n - 1
+  return 0
+
+print(countdown(3)) // expect: 3,2,1 then 0
+
+print("=== while test end ===")