more simplification

day01-easy/main.scm

@@ -22,29 +22,32 @@
     current
     (reduce (cdr list) reducer (reducer current (car list)))))
 
-(define (first-last-combine current rest)
+(define (combine list combiner)
   (if
-    (null? current)
-    rest
+    (null? (car list))
+    (cdr list)
     (if
-      (null? rest)
-      current
-      (cons (car current) (cdr rest)))))
+      (null? (cdr list))
+      (car list)
+      (combiner (car list) (cdr list)))))
+
+(define (sum numbers) (reduce numbers + 0))
+
+(define (is-numeric-char char) (if (char-numeric? char) #t #f))
 
 (define (first-last list predicate)
   (if
     (null? list)
     '()
-    (first-last-combine
+    (combine
+      (cons
         (if
           (predicate (car list))
           (cons (car list) (cons (car list) '()))
           '())
-      (first-last (cdr list) predicate))))
-
-(define (sum numbers) (reduce numbers + 0))
-
-(define (is-numeric-char char) (if (char-numeric? char) #t #f))
+        (first-last (cdr list) predicate))
+      (lambda (current rest)
+        (cons (car current) (cdr rest))))))
 
 (define (solve-line line)
   (