Testing early stop with options

mapoptiontest/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "mapoptiontest"
+version = "0.1.0"

mapoptiontest/Cargo.toml

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+[package]
+name = "mapoptiontest"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

mapoptiontest/README.md

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+# MapOptionTest
+
+Test how one can stop a collect when a map produces an option and the option is
+none.

mapoptiontest/src/main.rs

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+fn main() {
+    let all_evens = [2u8, 4, 6, 8];
+    let result: Result<Vec<_>, _> = all_evens
+        .iter()
+        .map(|value| if value % 2 == 0 { Some(value) } else { None })
+        .map(|opt| opt.ok_or(format!("Not good")))
+        .collect();
+    println!("All Evens: {:?}", result);
+
+    let not_evens = [2, 2, 2, 2, 2, 1];
+    let result: Result<Vec<_>, _> = not_evens
+        .iter()
+        .map(|value| if value % 2 == 0 { Some(value) } else { None })
+        .map(|opt| opt.ok_or(format!("Not good")))
+        .collect();
+    println!("Not Evens: {:?}", result);
+}