simplified compose

day01-easy/main.scm

@@ -12,20 +12,19 @@
 
 (define (id value) value)
 
-(define (compose result-transformer f argument-transformer)
-  (lambda (value)
-    (result-transformer (f (argument-transformer value)))))
-
 (define Y (lambda (f) (f (lambda (x) ((Y f) x)))))
 
 (define (reduce-right reducer initial) (Y
   (lambda (f) (lambda (list)
     (if (null? list) initial (reducer (car list) (f (cdr list))))))))
 
-(define (map mapper)
-  (reduce-right
-    (lambda (current accumulator) (cons (mapper current) accumulator))
-    '()))
+(define (map mapper) (reduce-right
+  (lambda (current accumulator) (cons (mapper current) accumulator))
+  '()))
+
+(define compose (reduce-right
+  (lambda (current accumulator) (lambda (value) (current (accumulator value))))
+  id))
 
 (define (combine combiner)
   (lambda (a b) (if (null? a) b (if (null? b) a (combiner a b)))))
@@ -36,20 +35,17 @@
   (lambda (f) (lambda (n)
     (if (= n 0) '() (cons value (f (- n 1))))))))
 
-(define (is-numeric-char char) (if (char-numeric? char) #t #f))
-
-(define (first-last predicate) (compose
-  id
+(define solve-line (compose (list
+  string->number
+  list->string
   (reduce-right
     (combine (lambda (left right) (cons (car left) (cdr right))))
     '())
-  (map (lambda (entry) (if (predicate entry) ((repeat entry) 2) '())))))
-
-(define solve-line (compose
-  (lambda (first-last-result) (string->number (list->string first-last-result)))
-  (first-last is-numeric-char)
-  string->list))
+  (map (lambda (char) (if (char-numeric? char) ((repeat char) 2) '())))
+  string->list)))
 
-(define (solve-all lines) (sum ((map solve-line) lines)))
+(define solve-all (compose (list
+  sum
+  (map solve-line))))
 
 (display (solve-all (read-lines)))