trying

library/css/math.rkt

@@ -0,0 +1,21 @@
+#lang racket/base
+(require "core.rkt")
+
+(struct cssq (num unit)   
+  #:methods gen:custom-write
+  [(define write-proc 
+     (λ(x port mode) (display (format "~a~a" (cssq-num x) (cssq-unit x)) port)))])
+
+(define (string->cssq str)
+  (apply cssq 
+         (let ([str (string-trim str "s" #:left? #f)])
+           (regexp-split #px"(?<=[.\\d])(?=[A-Za-z])" str))))
+
+
+(define (css+ left right)
+  (string->cssq (format "~a~a" (apply + (map string->number (list (cssq-num left) (cssq-num right))))(cssq-unit left))))
+
+(module+ main
+  (define q1 (string->cssq "51.2rems"))
+  (define q2 (string->cssq "10rem"))
+  (css+ q1 q2))