diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-1.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-1.rkt
index b71b148fe3..404d71033b 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-1.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-1.rkt
@@ -6,7 +6,7 @@
 ;; with commit: 4b848777d12a2e5b59b43c8e77f9f68b747d1151
 
 (require redex/reduction-semantics
-         math/base)
+         (only-in redex/private/generate-term pick-an-index))
 
 (provide (all-defined-out))
 
@@ -942,4 +942,4 @@
 
 
 (define (generate-enum-term)
-  (generate-term abort-lang e #:i-th (random-natural #e10e200)))
+  (generate-term abort-lang e #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-2.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-2.rkt
index a67b416f08..ba1796b1c0 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-2.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-2.rkt
@@ -3,7 +3,7 @@
 (define the-error "list/c contracts aren't applied properly in the cons case")
 
 (require redex/reduction-semantics
-         math/base)
+         (only-in redex/private/generate-term pick-an-index))
 
 (provide (all-defined-out))
 
@@ -940,4 +940,4 @@
 
 
 (define (generate-enum-term)
-  (generate-term abort-lang e #:i-th (random-natural #e10e200)))
+  (generate-term abort-lang e #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-3.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-3.rkt
index cc45f2cf7e..99d274cc18 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-3.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-3.rkt
@@ -3,7 +3,7 @@
 (define the-error "the function argument to call/comp has the wrong type")
 
 (require redex/reduction-semantics
-         math/base)
+         (only-in redex/private/generate-term pick-an-index))
 
 (provide (all-defined-out))
 
@@ -940,4 +940,4 @@
 
 
 (define (generate-enum-term)
-  (generate-term abort-lang e #:i-th (random-natural #e10e200)))
+  (generate-term abort-lang e #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-base.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-base.rkt
index 9144cc383f..a4b7dd2b2e 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-base.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/delim-cont/delim-cont-base.rkt
@@ -3,7 +3,7 @@
 (define the-error "no-error")
 
 (require redex/reduction-semantics
-         math/base)
+         (only-in redex/private/generate-term pick-an-index))
 
 (provide (all-defined-out))
 
@@ -937,4 +937,4 @@
   (judgment-holds (tc · · ,e t)))
 
 (define (generate-enum-term)
-  (generate-term abort-lang e #:i-th (random-natural #e10e200)))
+  (generate-term abort-lang e #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-1.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-1.rkt
index 080e6ef58c..211ee69636 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-1.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-1.rkt
@@ -3,9 +3,9 @@
 (define the-error "confuses the lhs value for the rhs value in cons type rule")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
-         racket/match
-         math/base)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -434,4 +434,4 @@
     [#f #f]))
 
 (define (generate-enum-term)
-  (generate-term list-machine-typing (l0 : ι p) #:i-th (random-natural #e10e200)))
+  (generate-term list-machine-typing (l0 : ι p) #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-2.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-2.rkt
index da7d3b6e13..a1053afe47 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-2.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-2.rkt
@@ -3,9 +3,9 @@
 (define the-error "var-set may skip a var with matching id (in reduction)")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
-         racket/match
-         math/base)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -434,4 +434,4 @@
     [#f #f]))
 
 (define (generate-enum-term)
-  (generate-term list-machine-typing (l0 : ι p) #:i-th (random-natural #e10e200)))
+  (generate-term list-machine-typing (l0 : ι p) #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-3.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-3.rkt
index a1dd59547b..d11994c700 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-3.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-3.rkt
@@ -3,9 +3,9 @@
 (define the-error "cons doesn't actually update the store")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
-         racket/match
-         math/base)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -430,4 +430,4 @@
     [#f #f]))
 
 (define (generate-enum-term)
-  (generate-term list-machine-typing (l0 : ι p) #:i-th (random-natural #e10e200)))
+  (generate-term list-machine-typing (l0 : ι p) #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-base.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-base.rkt
index 120256151b..f5950bfe89 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-base.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/list-machine/list-machine-base.rkt
@@ -3,9 +3,9 @@
 (define the-error "no error")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
-         racket/match
-         math/base)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -430,4 +430,4 @@
     [#f #f]))
 
 (define (generate-enum-term)
-  (generate-term list-machine-typing (l0 : ι p) #:i-th (random-natural #e10e200)))
+  (generate-term list-machine-typing (l0 : ι p) #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-10.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-10.rkt
index ddc7a1a816..802f1160f4 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-10.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-10.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-2.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-2.rkt
index a8a9a738b7..9295c9d689 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-2.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-2.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -279,4 +279,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-3.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-3.rkt
index 9feecff405..f882f15138 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-3.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-3.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-4.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-4.rkt
index 15ad7c3809..d38add8a6d 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-4.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-4.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-5.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-5.rkt
index c8c6832d22..7976bd56e0 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-5.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-5.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-6.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-6.rkt
index b6910ec76c..c840eb0d2c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-6.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-6.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-7.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-7.rkt
index bd2e236127..b708610baf 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-7.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-7.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -280,4 +280,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-8.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-8.rkt
index 4de83e5819..e684952d01 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-8.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-8.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-9.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-9.rkt
index 593d4d6024..10adf4a32c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-9.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-9.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-base.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-base.rkt
index 774456792b..111395ac02 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-base.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/poly-stlc/poly-stlc-base.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -281,4 +281,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term poly-stlc M #:i-th (random-natural #e10e200)))
+  (generate-term poly-stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-1.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-1.rkt
index ebe6b87d82..bc56894d39 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-1.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-1.rkt
@@ -3,8 +3,8 @@
 (define the-error "ins does no rebalancing")
 
 (require redex/reduction-semantics
-         racket/match
-         math/base)
+         (only-in redex/private/generate-term pick-an-index)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -290,4 +290,4 @@
       (ins-preserves-rb-tree t)))
 
 (define (generate-enum-term)
-  (generate-term rbtrees t #:i-th (random-natural #e10e200)))
+  (generate-term rbtrees t #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-2.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-2.rkt
index ed21199c5c..9efe31f832 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-2.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-2.rkt
@@ -3,8 +3,8 @@
 (define the-error "the first case is removed from balance")
 
 (require redex/reduction-semantics
-         racket/match
-         math/base)
+         (only-in redex/private/generate-term pick-an-index)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -288,4 +288,4 @@
       (ins-preserves-rb-tree t)))
 
 (define (generate-enum-term)
-  (generate-term rbtrees t #:i-th (random-natural #e10e200)))
+  (generate-term rbtrees t #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-3.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-3.rkt
index 73c75cc2d2..ae26468d7e 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-3.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-3.rkt
@@ -3,8 +3,8 @@
 (define the-error "doesn't increment black depth in non-empty case")
 
 (require redex/reduction-semantics
-         racket/match
-         math/base)
+         (only-in redex/private/generate-term pick-an-index)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -290,4 +290,4 @@
       (ins-preserves-rb-tree t)))
 
 (define (generate-enum-term)
-  (generate-term rbtrees t #:i-th (random-natural #e10e200)))
+  (generate-term rbtrees t #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-base.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-base.rkt
index cd755db2c8..9cbbce763a 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-base.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/rbtrees/rbtrees-base.rkt
@@ -3,8 +3,8 @@
 (define the-error "no-error")
 
 (require redex/reduction-semantics
-         racket/match
-         math/base)
+         (only-in redex/private/generate-term pick-an-index)
+         racket/match)
 
 (provide (all-defined-out))
 
@@ -290,4 +290,4 @@
       (ins-preserves-rb-tree t)))
 
 (define (generate-enum-term)
-  (generate-term rbtrees t #:i-th (random-natural #e10e200)))
+  (generate-term rbtrees t #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/1.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/1.diff
index ca1ee4ab47..5c153d216a 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/1.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/1.diff
@@ -1,18 +1,18 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "the order of the variable clauses is swapped")
 > 
-103,104d102
+104,105d103
 <   [(subst x x M)
 <    M]
-106a105,106
+107a106,107
 >   [(subst x x M)
 >    M]
-254a255
+255a256
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/2.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/2.diff
index 5a346d978b..3cac19e68f 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/2.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/2.diff
@@ -1,14 +1,14 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "only substitutes inside of hd constants")
 > 
-113,114c113,114
+114,115c114,115
 <   [(subst (c M) x M_x)
 <    (c (subst M x M_x))]
 ---
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/3.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/3.diff
index 0dd5753829..fe3b52434f 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/3.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/3.diff
@@ -1,16 +1,16 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "substitutes rator into rand in application")
 > 
-116c116
+117c117
 <    ((subst M x M_x) (subst N x M_x))]
 ---
 >    ((subst M x M_x) (subst N x M))]
-254a255
+255a256
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/4.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/4.diff
index fb1ca997eb..bdebba0522 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/4.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/4.diff
@@ -1,21 +1,21 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "substitutes inside of λ that binds the sub variable")
 > 
-107,108d106
+108,109d107
 <   [(subst (λ (x τ) M) x M_x)
 <    (λ (x τ) M)]
-113,114d110
+114,115d111
 <   [(subst (c M) x M_x)
 <    (c (subst M x M_x))]
-116a113,114
+117a114,115
 >   [(subst (c M) x M_x)
 >    (c (subst M x M_x))]
-254a253
+255a254
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/5.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/5.diff
index 08ded2a422..1881a73ce3 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/5.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/5.diff
@@ -1,12 +1,12 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "picks up the bound variable when recurring inside λ")
 > 
-253a254
+254a255
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/6.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/6.diff
index d16ba41951..cb47d8ae0d 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/6.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/6.diff
@@ -1,12 +1,12 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "swaps the bound var when recurring inside λ")
 > 
-253a254
+254a255
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/7.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/7.diff
index 05e0301030..d2327a5e2c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/7.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/7.diff
@@ -1,16 +1,16 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "swaps to/from expressions when recurring inside a constant")
 > 
-114c114
+115c115
 <    (c (subst M x M_x))]
 ---
 >    (c (subst M_x x M))]
-254a255
+255a256
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/8.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/8.diff
index e4f442586c..6b8b695819 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/8.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/8.diff
@@ -1,16 +1,16 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "swaps the order of the λ clauses")
 > 
-107,108d106
+108,109d107
 <   [(subst (λ (x τ) M) x M_x)
 <    (λ (x τ) M)]
-112a111,112
+113a112,113
 >   [(subst (λ (x τ) M) x M_x)
 >    (λ (x τ) M)]
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/9.diff b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/9.diff
index 4706728b62..e3b688338c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/9.diff
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/9.diff
@@ -1,18 +1,18 @@
 3,4d2
 < (define the-error "no error")
 < 
-6d3
+7d4
 <          racket/match
-7a5
+8a6
 >          racket/match
-11a10,11
+12a11,12
 > (define the-error "swaps to/from expressions when recurring in the rhs of app")
 > 
-111a112,113
+112a113,114
 >   [(subst (M N) x M_x)
 >    ((subst M_x x M) (subst N x M_x))]
-115,116d116
+116,117d117
 <   [(subst (M N) x M_x)
 <    ((subst M x M_x) (subst N x M_x))]
-254a255
+255a256
 > 
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-1.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-1.rkt
index 2249a82dcc..24e5b7a069 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-1.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-1.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -275,4 +276,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-2.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-2.rkt
index 808a1bfbcb..4a354ad19c 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-2.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-2.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -274,4 +275,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-3.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-3.rkt
index 4bde6efbf5..4cd59fe415 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-3.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-3.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -275,4 +276,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-4.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-4.rkt
index b0d5ca4032..00fa200c1d 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-4.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-4.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -273,4 +274,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-5.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-5.rkt
index df60e977a0..3667c49127 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-5.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-5.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -275,4 +276,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-6.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-6.rkt
index 18e40f2ad3..557544c3d7 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-6.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-6.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -275,4 +276,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-7.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-7.rkt
index 259225ba0d..1820470f00 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-7.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-7.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -275,4 +276,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-8.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-8.rkt
index ca89249d84..4f80fe57f7 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-8.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-8.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -274,4 +275,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-9.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-9.rkt
index dcb7df79c2..f43d78d1a7 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-9.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-9.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
@@ -275,4 +276,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-base.rkt b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-base.rkt
index 50ef10aa3c..d70066454f 100644
--- a/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-base.rkt
+++ b/pkgs/redex-pkgs/redex-examples/redex/examples/benchmark/stlc-sub/stlc-sub-base.rkt
@@ -3,6 +3,7 @@
 (define the-error "no error")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/match
          racket/list
          racket/contract
@@ -274,4 +275,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 dbe5b3f339..e86376aec3 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "app rule the range of the function is matched to the argument")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 58c58
 <    (typeof Γ M_2 σ)
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 347d7f9abd..f95109aa74 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "the order of the types in the function position of application has been swapped")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 57c57
 <   [(typeof Γ M (σ → σ_2))
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 200ffefceb..3f471d9554 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "the type of cons is incorrect")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 67c67
 <    (int → ((list int) → (list int)))]
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 bb06acc96c..8d7df681bf 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "the tail reduction returns the wrong value")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 92c92
 <         (in-hole E v_2)
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 b1b2a738ff..cb47557f2a 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "hd reduction acts on partially applied cons")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 88c88
 <    (--> (in-hole E (hd ((cons v_1) v_2)))
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 d8ed79c3ad..56b9367f2f 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "evaluation isn't allowed on the rhs of applications")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 36,37c36
 <      (E M)
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 cd0044085f..f92bbbd4b4 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "lookup always returns int")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 76c76
 <    σ]
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 a9f99c8d84..691e083eeb 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
@@ -2,9 +2,9 @@
 < (define the-error "no error")
 ---
 > (define the-error "variables aren't required to match in lookup")
-7d6
+8d7
 <          racket/contract
-8a8
+9a9
 >          racket/contract
 75c75
 <   [(lookup (x σ Γ) x)
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 0d96196038..7b091423a8 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
@@ -3,10 +3,10 @@
 (define the-error "app rule the range of the function is matched to the argument")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -251,4 +251,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 2f32bc46d6..554c940440 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
@@ -3,10 +3,10 @@
 (define the-error "the ((cons number) v) value has been omitted")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/contract
          racket/match
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -251,4 +251,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 1f39484d7d..f100577666 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
@@ -3,10 +3,10 @@
 (define the-error "the order of the types in the function position of application has been swapped")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -252,4 +252,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 48577f5737..4b3981cc90 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
@@ -3,10 +3,10 @@
 (define the-error "the type of cons is incorrect")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -252,4 +252,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 437ed7de71..f60ce40966 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
@@ -3,10 +3,10 @@
 (define the-error "the tail reduction returns the wrong value")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -251,4 +251,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 8b8155eb80..9080a48d73 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
@@ -3,10 +3,10 @@
 (define the-error "hd reduction acts on partially applied cons")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -251,4 +251,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 10dd18a235..52472fc106 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
@@ -3,10 +3,10 @@
 (define the-error "evaluation isn't allowed on the rhs of applications")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -250,4 +250,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 24be9124fa..4f4516fd25 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
@@ -3,10 +3,10 @@
 (define the-error "lookup always returns int")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -251,4 +251,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 7ff10e41ab..4c0d013104 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
@@ -3,10 +3,10 @@
 (define the-error "variables aren't required to match in lookup")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/match
          racket/contract
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -251,4 +251,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
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 52bb9b5ea2..ff3349be03 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
@@ -3,10 +3,10 @@
 (define the-error "no error")
 
 (require redex/reduction-semantics
+         (only-in redex/private/generate-term pick-an-index)
          racket/list
          racket/contract
          racket/match
-         math/base
          "tut-subst.rkt")
 
 (provide (all-defined-out))
@@ -252,4 +252,4 @@
           (equal? t-type (type-check (car red-res))))))))
 
 (define (generate-enum-term)
-  (generate-term stlc M #:i-th (random-natural #e10e200)))
+  (generate-term stlc M #:i-th (pick-an-index)))
diff --git a/pkgs/redex-pkgs/redex-lib/redex/private/generate-term.rkt b/pkgs/redex-pkgs/redex-lib/redex/private/generate-term.rkt
index b1f97906e3..3787ef9fb0 100644
--- a/pkgs/redex-pkgs/redex-lib/redex/private/generate-term.rkt
+++ b/pkgs/redex-pkgs/redex-lib/redex/private/generate-term.rkt
@@ -822,4 +822,5 @@
          exn:fail:redex:generation-failure?
          redex-generator
          (struct-out counterexample)
-         (struct-out exn:fail:redex:test))
+         (struct-out exn:fail:redex:test)
+         pick-an-index)