diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/10.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/10.diff
index e86376aec3..23bcc13828 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/10.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/10.diff
@@ -2,17 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "app rule the range of the function is matched to the argument")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 58c58
 <    (typeof Γ M_2 σ)
 ---
 >    (typeof Γ M_2 σ_2)
 232d231
 < 
-249c248
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/2.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/2.diff
index 0f1cb447ce..d024180321 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/2.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/2.diff
@@ -7,7 +7,3 @@
 <      ((cons v) v))
 ---
 >      (cons v))
-249c248
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/3.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/3.diff
index f95109aa74..1932a76597 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/3.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/3.diff
@@ -2,15 +2,7 @@
 < (define the-error "no error")
 ---
 > (define the-error "the order of the types in the function position of application has been swapped")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 57c57
 <   [(typeof Γ M (σ → σ_2))
 ---
 >   [(typeof Γ M (σ_2 → σ))
-249c249
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/4.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/4.diff
index 3f471d9554..1cebcca1f5 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/4.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/4.diff
@@ -2,15 +2,7 @@
 < (define the-error "no error")
 ---
 > (define the-error "the type of cons is incorrect")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 67c67
 <    (int → ((list int) → (list int)))]
 ---
 >    (int → ((list int) → int))]
-249c249
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/5.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/5.diff
index 8d7df681bf..dd35b1299c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/5.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/5.diff
@@ -2,17 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "the tail reduction returns the wrong value")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 92c92
 <         (in-hole E v_2)
 ---
 >         (in-hole E v_1)
 232d231
 < 
-249c248
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/6.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/6.diff
index cb47557f2a..c978fe3fba 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/6.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/6.diff
@@ -2,17 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "hd reduction acts on partially applied cons")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 88c88
 <    (--> (in-hole E (hd ((cons v_1) v_2)))
 ---
 >    (--> (in-hole E (hd (cons v_1)))
 232d231
 < 
-249c248
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/7.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/7.diff
index 56b9367f2f..5df0c31c62 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/7.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/7.diff
@@ -2,10 +2,6 @@
 < (define the-error "no error")
 ---
 > (define the-error "evaluation isn't allowed on the rhs of applications")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 36,37c36
 <      (E M)
 <      (v E)))
@@ -13,7 +9,3 @@
 >      (E M)))
 232d230
 < 
-249c247
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/8.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/8.diff
index f92bbbd4b4..d18e4f37b9 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/8.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/8.diff
@@ -2,17 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "lookup always returns int")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 76c76
 <    σ]
 ---
 >    int]
 232d231
 < 
-249c248
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/9.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/9.diff
index 691e083eeb..99aaad3984 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/9.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/9.diff
@@ -2,17 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "variables aren't required to match in lookup")
-8d7
-<          racket/contract
-9a9
->          racket/contract
 75c75
 <   [(lookup (x σ Γ) x)
 ---
 >   [(lookup (x σ Γ) x_2)
 232d231
 < 
-249c248
-<          (= (length red-res) 1) 
----
->          (= (length red-res) 1)
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-10.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-10.rkt
index c940da175e..6194c5ae97 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-10.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-10.rkt
@@ -264,15 +264,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-2.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-2.rkt
index 13f0e6afa4..b48aa96393 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-2.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-2.rkt
@@ -5,8 +5,8 @@
 (require redex/reduction-semantics
          (only-in redex/private/generate-term pick-an-index)
          racket/list
-         racket/contract
          racket/match
+         racket/contract
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -264,15 +264,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-3.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-3.rkt
index 661e9b0b1f..5615fa769f 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-3.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-3.rkt
@@ -265,15 +265,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-4.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-4.rkt
index dc10d2e32a..06e5de57dd 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-4.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-4.rkt
@@ -265,15 +265,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-5.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-5.rkt
index ba02a3c960..10bfba6605 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-5.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-5.rkt
@@ -264,15 +264,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-6.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-6.rkt
index ca6e4d85c4..7e7d7d1be3 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-6.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-6.rkt
@@ -264,15 +264,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-7.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-7.rkt
index 9bbf08d565..9360bee92f 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-7.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-7.rkt
@@ -263,15 +263,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-8.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-8.rkt
index ee843474c0..8ee7b2cf14 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-8.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-8.rkt
@@ -264,15 +264,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-9.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-9.rkt
index 69a31f0014..6aaf98f71c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-9.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-9.rkt
@@ -264,15 +264,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-base.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-base.rkt
index d790961584..b62eeaeb1c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-base.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc/stlc-base.rkt
@@ -5,8 +5,8 @@
 (require redex/reduction-semantics
          (only-in redex/private/generate-term pick-an-index)
          racket/list
-         racket/contract
          racket/match
+         racket/contract
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -247,7 +247,7 @@
             [t-type (type-check term)])
         ;; xxx shouldn't this be t-type IMPLIES this?
         (and
-         (= (length red-res) 1) 
+         (= (length red-res) 1)
          (or 
           (equal? (car red-res) "error")
           (equal? t-type (type-check (car red-res))))))))
@@ -265,15 +265,21 @@
 (define fixed
   (term
    (;; 2
-    ((cons 1) 2)
+    ((cons 1) nil)
     ;; 3
-    ((λ (x int) (hd x))
+    ((λ (x (list int)) 1) 
      7)
+    ;; 4 (if we hadn't changed number->v in cons)
+    (cons ((cons 0) nil))
+    ;; 5
+    (tl ((cons 1) nil))
+    ;; 6
+    (hd ((cons 1) nil))
+    ;; 7
+    ((λ (x int) x) (hd ((cons 1) nil)))
+    ;; 8
+    ((λ (x (list int)) (cons x)) nil)
+    ;; 9
+    ((λ (x int) (λ (y (list int)) x)) 1)
     ;; 10
-    ((λ (x (list int)) (hd x))
-     7)
-    ;; 5, 6, 7, 8, 9
-    ((λ (x int) (hd x))
-     ((cons 1) nil))
-    ;; 4
-    (hd ((cons ((cons 1) nil)) nil)))))
+    (hd 0))))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/test-file.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/test-file.rkt
index 920f33b572..e86db5285b 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/test-file.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/test-file.rkt
@@ -189,7 +189,7 @@
     [(equal? gen-type 'fixed)
      (define some-failed?
        (for/or ([t (in-list fixed)])
-         (define ok? (check t))
+         (define ok? (check (and (tc t) t)))
          (not ok?)))
      (unless some-failed?
        (error 'fixed "Expected some term to fail, but didn't find one in ~a" fixed))]
@@ -240,13 +240,14 @@
   (for ([gen-type (in-list types)])
     (test-file filename verbose #f gen-type (* minutes 60))))
 
-(call-with-output-file output-file
-  (λ (out)
-    (write
-     (apply append
-            (for/list ([(type times) (in-hash results)])
-              (apply append
-                     (for/list ([t times])
-                       (list filename type t)))))
+(unless (member 'fixed types)
+  (call-with-output-file output-file
+    (λ (out)
+      (write
+       (apply append
+              (for/list ([(type times) (in-hash results)])
+                (apply append
+                       (for/list ([t times])
+                         (list filename type t)))))
      out))
-  #:exists 'replace)
+    #:exists 'replace))