guide clarifications, but order for step5 tests.

process/guide.md

@@ -770,8 +770,8 @@ diff -urp ../process/step4_if_fn_do.txt ../process/step5_tco.txt
     `EVAL`) to be the second `ast` argument. Continue at the beginning
     of the loop (no return).
   * `do`: change the `eval_ast` call to evaluate all the parameters
-    the except for the last (2nd list element up to but not
-    including last). Set `ast` to the last element of `ast`. Continue
+    except for the last (2nd list element up to but not including
+    last). Set `ast` to the last element of `ast`. Continue
     at the beginning of the loop (`env` stays unchanged).
   * `if`: the condition continues to be evaluated, however, rather
     than evaluating the true or false branch, `ast` is set to the
@@ -781,21 +781,21 @@ diff -urp ../process/step4_if_fn_do.txt ../process/step5_tco.txt
 * The return value from the `fn*` special form will now become an
   object/structure with attributes that allow the default invoke case
   of `EVAL` to do TCO on mal functions. Those attributes are:
-  * `fn`: the original function value return in step 4 (this is
-    actually deferrable until step 9 when it is needed for the `map`
-    and `apply` core functions).
   * `ast`: the second `ast` argument (third list element) representing
     the body of the function.
   * `params`: the first `ast` argument (second list element)
     representing the parameter names of the function.
   * `env`: the current value of the `env` parameter of `EVAL`.
+  * `fn`: the original function value (i.e. what was return by `fn*`
+    in step 4). Note that this is deferrable until step 9 when it is
+    needed for the `map` and `apply` core functions).
 
 * The default "apply"/invoke case of `EVAL` must now be changed to
   account for the new object/structure returned by the `fn*` form.
   Continue to call `eval_ast` on `ast`. The first element is `f`.
   Switch on the type of `f`:
   * regular function (not one defined by `fn*`): apply/invoke it as
-  * before (in step 4).
+    before (in step 4).
   * a `fn*` value: set `ast` to the `ast` attribute of `f`. Generate
     a new environment using the `env` and `params` attributes of `f`
     as the `outer` and `binds` arguments and rest `ast` arguments

tests/step5_tco.mal

@@ -1,17 +1,3 @@
-;; Test recursive non-tail call function
-
-(def! sum-to (fn* (n) (if (= n 0) 0 (+ n (sum-to (- n 1))))))
-
-(sum-to 10)
-;=>55
-
-;;; no try* yet, so test completion of side-effects
-(def! res1 nil)
-;=>nil
-(def! res1 (sum-to 10000))
-res1
-;=>nil
-
 ;; Testing recursive tail-call function
 
 (def! sum2 (fn* (n acc) (if (= n 0) acc (sum2 (- n 1) (+ n acc)))))
@@ -25,3 +11,20 @@ res1
 res2
 ;=>50005000
 
+
+;; Test recursive non-tail call function
+
+(def! sum-to (fn* (n) (if (= n 0) 0 (+ n (sum-to (- n 1))))))
+
+(sum-to 10)
+;=>55
+
+;;; no try* yet, so test completion of side-effects
+(def! res1 nil)
+;=>nil
+;;; For implementations without their own TCO this should fail and
+;;; leave res1 unchanged
+(def! res1 (sum-to 10000))
+res1
+;=>nil
+