Add apply procedure

preserves.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "3.3.2" # versioned in git, this version is just to confuse nimble
+version       = "99999999"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"

src/preserves.nim

@@ -1043,6 +1043,22 @@ when isMainModule:
   var pr = t.toPreserveHook(void)
   assert fromPreserveHook(t, pr)
 
+proc apply*[E](result: var Preserve[E]; op: proc(_: var Preserve[E])) =
+  proc recurse(result: var Preserve[E]) = apply(result, op)
+  op(result)
+  case result.kind
+  of pkBoolean, pkFloat, pkDouble, pkSignedInteger, pkString, pkByteString, pkSymbol, pkEmbedded: discard
+  of pkRecord:
+    apply(result.record, recurse)
+  of pkSequence:
+    apply(result.sequence, recurse)
+  of pkSet:
+    apply(result.set, recurse)
+  of pkDictionary:
+    apply(result.dict) do (e: var DictEntry[E]):
+      recurse(e.key)
+      recurse(e.val)
+
 proc mapEmbeds*(pr: sink Preserve[void]; E: typedesc): Preserve[E] =
   ## Convert `Preserve[void]` to `Preserve[E]` using `fromPreserve` for `E`.
   when E is void: {.error: "E cannot be void".}