From 334f11c5167402d43d0d7e52110e61ecba20ded0 Mon Sep 17 00:00:00 2001
From: Peter Saxton <peterhsaxton@gmail.com>
Date: Wed, 2 Dec 2020 16:42:37 +0000
Subject: implement a lazy or function

---
 src/gleam/result.gleam | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

(limited to 'src')

diff --git a/src/gleam/result.gleam b/src/gleam/result.gleam
index 2ebf2ef..76ee0e1 100644
--- a/src/gleam/result.gleam
+++ b/src/gleam/result.gleam
@@ -202,6 +202,29 @@ pub fn or(first: Result(a, e), second: Result(a, e)) -> Result(a, e) {
   }
 }
 
+/// Return the first value if it is Ok, otherwise evaluates the given function for a fallback value.
+///
+/// ## Examples
+///
+///    > or(Ok(1), Ok(2))
+///    Ok(1)
+///
+///    > or(Ok(1), Error("Error 2"))
+///    Ok(1)
+///
+///    > or(Error("Error 1"), Ok(2))
+///    Ok(2)
+///
+///    > or(Error("Error 1"), Error("Error 2"))
+///    Error("Error 2")
+///
+pub fn lazy_or(first: Result(a, e), second: fn() -> Result(a, e)) -> Result(a, e) {
+  case first {
+    Ok(_) -> first
+    Error(_) -> second()
+  }
+}
+
 /// Combine a list of results into a single result.
 /// If all elements in the list are Ok then returns an Ok holding the list of values.
 /// If any element is Error then returns the first error.
-- 
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