Document opaque types

Closes https://github.com/gleam-lang/language-tour/issues/63

1 files changed, 38 insertions, 0 deletions

diff --git a/src/content/chapter5_advanced_features/lesson01_use/code.gleam b/src/content/chapter5_advanced_features/lesson01_use/code.gleam
new file mode 100644
index 0000000..e7b435b
--- /dev/null
+++ b/src/content/chapter5_advanced_features/lesson01_use/code.gleam
@@ -0,0 +1,38 @@
+import gleam/io
+import gleam/result
+
+pub fn main() {
+  io.debug(without_use())
+  io.debug(with_use())
+}
+
+pub fn without_use() {
+  result.try(get_username(), fn(username) {
+    result.try(get_password(), fn(password) {
+      result.map(log_in(username, password), fn(greeting) {
+        greeting <> ", " <> username
+      })
+    })
+  })
+}
+
+pub fn with_use() {
+  use username <- result.try(get_username())
+  use password <- result.try(get_password())
+  use greeting <- result.map(log_in(username, password))
+  greeting <> ", " <> username
+}
+
+// Here are some pretend functions for this example:
+
+fn get_username() {
+  Ok("alice")
+}
+
+fn get_password() {
+  Ok("hunter2")
+}
+
+fn log_in(_username: String, _password: String) {
+  Ok("Welcome")
+}