LLM approve #1

lib/base.tri

@@ -119,6 +119,47 @@ maybeBind m f = matchMaybe nothing f m
 maybeOr default m = matchMaybe default id m
 maybe? = matchMaybe false (_ : true)
 
+-- ---------------------------------------------------------------------------
+-- Lazy eliminators
+--
+-- A strict eliminator evaluates both branches because they are ordinary
+-- arguments. Give a branch that recurses, looks something up, or builds
+-- structure to one of these instead: it becomes a thunk and only the selected
+-- branch is ever applied.
+-- ---------------------------------------------------------------------------
+
+lazyBool = (thenK elseK cond :
+  ((chosen : chosen t)
+   (matchBool
+     thenK
+     elseK
+     cond)))
+
+-- This module has no list matcher, so `triage` is used directly: a cons is a
+-- Fork, which is why the cons case sits in the fork slot, exactly as in
+-- `matchList` in lib/list.tri.
+lazyList = (nilK consK xs :
+  ((chosen : chosen t)
+   (triage
+     nilK
+     _
+     (h r : (_ : consK h r))
+     xs)))
+
+lazyMaybe = (noneK someK m :
+  ((chosen : chosen t)
+   (matchMaybe
+     noneK
+     (x : (_ : someK x))
+     m)))
+
+lazyResult = (errK okK result :
+  ((chosen : chosen t)
+   (matchResult
+     (code rest : (_ : errK code rest))
+     (value rest : (_ : okK value rest))
+     result)))
+
 -- ---------------------------------------------------------------------------
 -- Basic arithmetic
 -- ---------------------------------------------------------------------------
@@ -217,7 +258,3 @@ resultMapErr = (f result :
     (code rest : err (f code) rest)
     (value rest : ok value rest)
     result)
-
--- ---------------------------------------------------------------------------
--- View facts
--- ---------------------------------------------------------------------------