Also add disclaimer on string.from_bytearray

lib/aiken/string.ak

@@ -26,9 +26,15 @@ test concat_3() {
 
 /// Convert a `ByteArray` into a `String`
 ///
+/// <br/>⚠️<pre>WARNING</pre> | This functions fails if the underlying `ByteArray` isn't UTF-8-encoded. <br/>In particular, you cannot convert arbitrary hash digests using this function. <br/>For converting arbitrary `ByteArray`s, use [bytearray.to_hex](../bytearray.html#to_hex).
+/// ---                  | ---
+///
 /// ```aiken
 /// string.from_bytearray("foo") == @"foo"
+///
 /// string.from_bytearray(#"666f6f") == @"foo"
+///
+/// string.from_bytearray(some_hash) -> fail
 /// ```
 pub fn from_bytearray(bytes: ByteArray) -> String {
   decode_utf8(bytes)

lib/scratchpad.ak

@@ -0,0 +1,24 @@
+use aiken/bytearray.{concat, push}
+use aiken/cbor
+
+pub fn serialise_int(value: Int) -> ByteArray {
+  let bytes =
+    #""
+      |> push(value) // >> 0
+      |> push(value / 256) // >> 8
+      |> push(value / 65536) // >> 16
+      |> push(value / 16777216)
+  bytes
+}
+
+pub fn serialise_long(value: Int) -> ByteArray {
+  serialise_int(value / 4294967296) |> concat(serialise_int(value))
+}
+
+test serialise_long_1() {
+  serialise_long(10737418240) == #"0000000280000000"
+}
+
+test serialise_builtin() {
+  cbor.serialise(10737418240) == #"1b0000000280000000"
+}