Add "upply" (U-shaped apply, names are hard)

d-.scm

@@ -12,6 +12,7 @@
    partial
    argmin
    iterate
+   upply
    generator
    macro-expand))
 
@@ -72,6 +73,10 @@
       v
       (iterate (1- n) f (f v))))
 
+(define (upply a b cmp . fs)
+  (let ([arm-f (apply compose fs)])
+    (cmp (arm-f a) (arm-f b))))
+
 ;; Shamelessly ripped from https://wingolog.org/archives/2013/02/25/on-generators
 (define (make-generator f)
   (define tag (make-prompt-tag))

test.scm

@@ -64,6 +64,11 @@
     (define value (iterate 2 1+ 3))
     (assert-equal 5 value)))
 
+(define-test-suite "upply"
+  (define-test "test"
+    (define value (upply -3 5 = abs 1-))
+    (assert-equal #t value)))
+
 (define-test-suite "generator"
   (define-test "test"
     (define number-generator