diff --git a/eg/rudiments/README.md b/eg/rudiments/README.md
index 51230f4..0567477 100644
--- a/eg/rudiments/README.md
+++ b/eg/rudiments/README.md
@@ -1,7 +1,8 @@
 This directory contains example sources which demonstrate
 the rudiments of SixtyPical.
 
-Some are meant to fail and produce an error message.
+Examples that are meant to fail and produce an error message
+are in the `errorful/` subdirectory.
 
 They are not meant to be specific to any architecture, but
 many do assume the existence of a routine at 65490 which
diff --git a/eg/rudiments/errorful/README.md b/eg/rudiments/errorful/README.md
new file mode 100644
index 0000000..e5b307a
--- /dev/null
+++ b/eg/rudiments/errorful/README.md
@@ -0,0 +1,4 @@
+This directory contains example SixtyPical sources which
+are intentionally invalid (for demonstration purposes)
+and are expected to elicit an error message from a
+SixtyPical implementation.
diff --git a/eg/rudiments/add-fail.60p b/eg/rudiments/errorful/add.60p
similarity index 100%
rename from eg/rudiments/add-fail.60p
rename to eg/rudiments/errorful/add.60p
diff --git a/eg/rudiments/range-error.60p b/eg/rudiments/errorful/range.60p
similarity index 100%
rename from eg/rudiments/range-error.60p
rename to eg/rudiments/errorful/range.60p
diff --git a/eg/rudiments/bad-vector.60p b/eg/rudiments/errorful/vector.60p
similarity index 100%
rename from eg/rudiments/bad-vector.60p
rename to eg/rudiments/errorful/vector.60p
diff --git a/eg/rudiments/vector-table.60p b/eg/rudiments/vector-table.60p
index 4362012..b6cce2a 100644
--- a/eg/rudiments/vector-table.60p
+++ b/eg/rudiments/vector-table.60p
@@ -3,6 +3,14 @@
 // Prints "AABAB".
 //
 
+// TODO: this doesn't pass the analyzer currently, which suggests a bug.
+//
+//     RangeExceededError: Possible range of x:byte (0, 255) exceeds
+//     acceptable range of vectors:vector table[32] (0, 31) (in main, line 57)
+//
+// (despite various attempts to work around by calling a setup routine, etc.)
+// It should really be able to figure out that the range of x is 0..4 there.
+
 vector routine
   trashes a, z, n
     print
@@ -49,10 +57,8 @@ define main routine
     copy printb, vectors + x
 
     ld x, 0
-    repeat {
+    for x up to 4 {
         copy vectors + x, print
         call print
-        inc x
-        cmp x, 5
-    } until z
+    }
 }