Add example of writing a file

Author: pranav1344

examples/lib/WriteFile.sml

@@ -0,0 +1,24 @@
+structure WriteFile:
+sig
+  val writeBinSeq: {filename: string, content: Word8.word Seq.t} -> unit
+end =
+struct
+
+  fun writeBinSeq {filename, content} =
+    let
+      val n = Seq.length content
+      val {file, file_size = oldSize} = MPL.File.openFileWriteable filename n
+      val k = 10000
+      val m = 1 + (n-1) div k
+    in
+      ForkJoin.parfor 1 (0, m) (fn i =>
+        let 
+          val lo = i*k
+          val hi = Int.min ((i+1)*k, n)
+        in
+          MPL.File.writeWord8s { file = file , file_offset = oldSize + lo, offset = 0} (Seq.subseq content (lo, hi-lo))
+        end
+        );
+      MPL.File.closeFile file
+    end
+end