Add valid/unvalid type, replacement of optional

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/DATS/valid.dats b/lib/DATS/valid.dats
new file mode 100644
index 0000000..f4ea0aa
--- /dev/null
+++ b/lib/DATS/valid.dats
@@ -0,0 +1,15 @@
+#define ATS_DYNLOADFLAG 0
+staload "lib/SATS/valid.sats"
+
+assume valid(a:t@ype,b:bool) = (a,bool b) 
+
+implement{a} create_valid(value : a) = (value,true)
+
+// Create unvalid value by casting null pointer to type.
+implement{a} create_unvalid() = let
+  staload UN = "prelude/SATS/unsafe.sats"
+in
+  ($UN.ptr0_get<a>(the_null_ptr),false) //UNSAFE:
+end
+
+implement{a} unwrap_valid(v) = v.0