Use mapcat FTW!

exercises/practice/raindrops/.meta/raindrops.ys

@@ -3,12 +3,5 @@
 dict =:: { 3: Pling, 5: Plang, 7: Plong }
 
 defn convert(number):
-  words =:
-    reduce _ [] [3 5 7]:
-      fn(acc num):
-        concat acc:
-          when (number % num).!: -[dict.$num]
-
-  if words.?:
-    str: words*
-    str: number
+  words =: mapcat(\((number % _).! &&& dict.get(_)) [3 5 7])
+  if words.?: str(words*) str(number)

exercises/practice/sum-of-multiples/.meta/sum-of-multiples.ys

@@ -1,8 +1,4 @@
 !yamlscript/v0
 
 defn sum(factors limit):
-  std/sum:
-    reduce _ [] factors:
-      fn(nums num):
-        when(num.? range(num limit num)):
-          .concat(nums).distinct()
+  factors.mapcat(\(when(_.? range(_ limit _))) _).distinct().std/sum()