test: Add example using options

There is currently no way to assert that an option value is None. We can
match option values, but we cannot write failing branches. I will add
something like is_none and potentially panic! in a future PR.

Also order the example programs lexicographically.

Author: uncomputable

example_progs/option.simf

@@ -0,0 +1,11 @@
+fn checked_div_32(x: u32, y: u32) -> Option<u32> {
+    match jet_is_zero_32(y) {
+        true  => None,
+        false => Some(jet_divide_32(x, y)),
+    }
+}
+
+fn main() {
+    let res: Option<u32> = checked_div_32(10, 3);
+    jet_verify(jet_eq_32(3, unwrap(res)));
+}

src/lib.rs

@@ -63,7 +63,6 @@ mod tests {
     #[test]
     fn test_progs() {
         for (prog_file, wit_file) in [
-            ("add.simf", "empty.wit"),
             ("add.simf", "empty.wit"),
             ("array.simf", "empty.wit"),
             ("cat.simf", "empty.wit"),
@@ -72,9 +71,11 @@ mod tests {
                 "checksigfromstackverify.wit",
             ),
             ("ctv.simf", "empty.wit"),
+            ("function.simf", "empty.wit"),
             ("list.simf", "empty.wit"),
             ("match.simf", "empty.wit"),
             ("nesting.simf", "empty.wit"),
+            ("option.simf", "empty.wit"),
             ("recursive-covenant.simf", "empty.wit"),
             ("scopes.simf", "empty.wit"),
             ("sighash_all.simf", "empty.wit"),
@@ -85,7 +86,6 @@ mod tests {
             ("sighash_none.simf", "sighash_none.wit"),
             ("tuple.simf", "empty.wit"),
             ("unwrap.simf", "empty.wit"),
-            ("function.simf", "empty.wit"),
         ] {
             _test_progs(prog_file, wit_file)
         }