From eacb0df9d77c339a079cf9e376aaff6c659e0447 Mon Sep 17 00:00:00 2001
From: Jason Walker <jason0@pm.me>
Date: Mon, 2 Dec 2024 19:45:35 -0500
Subject: [PATCH] Add from-optional function

---
 library/optional.lisp | 8 ++++++++
 library/prelude.lisp  | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/library/optional.lisp b/library/optional.lisp
index 7e38a3c00..4a001194b 100644
--- a/library/optional.lisp
+++ b/library/optional.lisp
@@ -7,6 +7,7 @@
    (#:cell #:coalton-library/cell)
    (#:iter #:coalton-library/iterator))
   (:export
+   #:from-optional
    #:from-some
    #:some?
    #:none?))
@@ -23,6 +24,13 @@
   ;; Optional
   ;;
 
+  (declare from-optional (:a -> (Optional :a) -> :a))
+  (define (from-optional def opt)
+    "Get the value of OPT, or return DEF if OPT is None."
+    (match opt
+      ((Some x) x)
+      ((None) def)))
+
   (declare from-some (String -> (Optional :a) -> :a))
   (define (from-some str opt)
     "Get the value of OPT, erroring with the provided string if it is None."
diff --git a/library/prelude.lisp b/library/prelude.lisp
index f7756e22c..937d86e6f 100644
--- a/library/prelude.lisp
+++ b/library/prelude.lisp
@@ -130,10 +130,12 @@
 
   (:import-from
    #:coalton-library/optional
+   #:from-optional
    #:from-some
    #:some?
    #:none?)
   (:export
+   #:from-optional
    #:from-some
    #:some?
    #:none?)