Add pop for dictionaries

preserves.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version = "20231028"
+version = "20231102"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"

src/preserves.nim

@@ -284,6 +284,18 @@ proc getOrDefault(pr: Preserve; key: Preserve): Preserve =
         result = v
         break
 
+proc pop*(pr: var Preserve; key: Preserve; val: var Preserve): bool =
+  ##  Deletes the `key` from a Preserves dictionary.
+  ## Returns true, if the key existed, and sets `val` to the mapping
+  ## of the key. Otherwise, returns false, and the `val` is unchanged.
+  if pr.kind == pkDictionary:
+    var i = 0
+    while i < pr.dict.len:
+      if pr.dict[i].key == key:
+        val = move pr.dict[i].val
+        delete(pr.dict, i, i)
+        return true
+
 proc incl*(pr: var Preserve; key: Preserve) =
   ## Include `key` in the Preserves set `pr`.
   for i in 0..pr.set.high:
@@ -638,7 +650,6 @@ proc encode*[E](pr: Preserve[E]): seq[byte] =
   s.write pr
   result = cast[seq[byte]](move s.data)
 
-
 proc decodePreserves*(s: Stream; E = void): Preserve[E] =
   ## Decode a Preserves value from a binary-encoded stream.
   if s.atEnd: raise newException(IOError, "End of Preserves stream")