"999 is enough for anybody" triple-zero padding (#18)

When I hit 999 exercises, I will finally have reached the ultimate
state of soteriological release and no more exercises will be needed.
The cycle will be complete. All that will be left is perfect quietude,
freedom, and highest happiness.

exercises/025_errors5.zig

@@ -0,0 +1,38 @@
+//
+// Zig has a handy "try" shortcut for this common error handling pattern:
+//
+//     canFail() catch |err| return err;
+//
+// which can be more compactly written as:
+//
+//     try canFail();
+//
+const std = @import("std");
+
+const MyNumberError = error{
+    TooSmall,
+    TooBig,
+};
+
+pub fn main() void {
+    var a: u32 = addFive(44) catch 0;
+    var b: u32 = addFive(14) catch 0;
+    var c: u32 = addFive(4) catch 0;
+
+    std.debug.print("a={}, b={}, c={}", .{ a, b, c });
+}
+
+fn addFive(n: u32) MyNumberError!u32 {
+    // This function needs to return any error which might come back from detect().
+    // Please use a "try" statement rather than a "catch".
+    //
+    var x = detect(n);
+
+    return x + 5;
+}
+
+fn detect(n: u32) MyNumberError!u32 {
+    if (n < 10) return MyNumberError.TooSmall;
+    if (n > 20) return MyNumberError.TooBig;
+    return n;
+}