mk: everyo / someo — predicate-style relations

(everyo rel l): every element of l satisfies the unary relation rel.
(someo rel l): some element does. Both compose with intarith and other
predicate-shaped goals:
  (everyo (fn (x) (lto-i x 10)) (list 1 5 9))    -> succeeds
  (someo  (fn (x) (lto-i 100 x)) (list 5 50 200)) -> succeeds

10 new tests, 310/310 cumulative.

lib/minikanren/relations.sx

@@ -140,3 +140,19 @@
     (conde
       ((nullo l1) (nullo l2))
       ((fresh (a d a-prime d-prime) (conso a d l1) (conso a-prime d-prime l2) (rel a a-prime) (mapo rel d d-prime))))))
+
+(define
+  everyo
+  (fn
+    (rel l)
+    (conde
+      ((nullo l))
+      ((fresh (a d) (conso a d l) (rel a) (everyo rel d))))))
+
+(define
+  someo
+  (fn
+    (rel l)
+    (conde
+      ((fresh (a d) (conso a d l) (rel a)))
+      ((fresh (a d) (conso a d l) (someo rel d))))))

lib/minikanren/tests/predicates.sx

@@ -0,0 +1,87 @@
+;; lib/minikanren/tests/predicates.sx — everyo, someo.
+
+;; --- everyo ---
+
+(mk-test
+  "everyo-empty-trivially-true"
+  (run* q (everyo (fn (x) (== x 1)) (list)))
+  (list (make-symbol "_.0")))
+
+(mk-test
+  "everyo-all-match"
+  (run*
+    q
+    (everyo
+      (fn (x) (== x 1))
+      (list 1 1 1)))
+  (list (make-symbol "_.0")))
+
+(mk-test
+  "everyo-some-mismatch"
+  (run*
+    q
+    (everyo
+      (fn (x) (== x 1))
+      (list 1 2 1)))
+  (list))
+
+(mk-test
+  "everyo-with-intarith"
+  (run*
+    q
+    (everyo
+      (fn (x) (lto-i x 10))
+      (list 1 5 9)))
+  (list (make-symbol "_.0")))
+
+(mk-test
+  "everyo-with-intarith-fail"
+  (run*
+    q
+    (everyo
+      (fn (x) (lto-i x 5))
+      (list 1 5 9)))
+  (list))
+
+;; --- someo ---
+
+(mk-test
+  "someo-finds-element"
+  (run*
+    q
+    (someo
+      (fn (x) (== x 2))
+      (list 1 2 3)))
+  (list (make-symbol "_.0")))
+
+(mk-test
+  "someo-not-found"
+  (run*
+    q
+    (someo
+      (fn (x) (== x 99))
+      (list 1 2 3)))
+  (list))
+
+(mk-test
+  "someo-empty-fails"
+  (run* q (someo (fn (x) (== x 1)) (list)))
+  (list))
+
+(mk-test
+  "someo-multiple-matches-yields-multiple"
+  (let
+    ((res (run* q (fresh (x) (someo (fn (y) (== y x)) (list 1 2 1)) (== q x)))))
+    (len res))
+  3)
+
+(mk-test
+  "someo-with-intarith"
+  (run*
+    q
+    (someo
+      (fn (x) (lto-i 100 x))
+      (list 5 50 200)))
+  (list (make-symbol "_.0")))
+
+(mk-tests-run!)

plans/minikanren-on-sx.md

@@ -173,6 +173,11 @@ _(none yet)_
 
 _Newest first._
 
+- **2026-05-08** — **everyo / someo (predicate-style relations)**:
+  `(everyo rel l)` — every element of l satisfies rel; `(someo rel l)` —
+  some element does. Both compose with intarith for numeric tests:
+  `(everyo (fn (x) (lto-i x 10)) (list 1 5 9))` succeeds. 10 new tests,
+  310/310 cumulative.
 - **2026-05-08** — **mapo (relational map) — 300 test milestone**: `(mapo
   rel l1 l2)` succeeds when l2 is l1 with each element rel-related. Works
   forward and backward; composes with intarith — `(mapo (fn (a b) (*o-i