Add valid/unvalid type, replacement of optional

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/SATS/valid.sats b/lib/SATS/valid.sats
new file mode 100644
index 0000000..e3841e0
--- /dev/null
+++ b/lib/SATS/valid.sats
@@ -0,0 +1,18 @@
+
+// implement a type that can be unvalid or valid. 
+// It's a replacement of Optional, but can be allocated on stack, so no heap allocaton needed.
+// When unvalid, it should be not possible to get unvalid value, thats why abstract type is used.
+// bool b: true means valid, false unvalid
+abst@ype valid(a:t@ype,b:bool) = (a,bool b)
+
+typedef Valid(a:t@ype) = [b : bool] valid(a,b) 
+
+// Wraps valid value.
+fn {a:t@ype} create_valid(value : a) : valid(a,true)
+
+// Creates unvalid type.
+fn {a:t@ype} create_unvalid() : valid(a,false)
+
+// Only function that allows getting value. Only accepts valid values. 
+fn {a:t@ype} unwrap_valid(valid(a,true)) : a
+