Rename

2 files changed, 69 insertions, 0 deletions

diff --git a/src/content/chapter5_advanced_features/lesson00_use/code.gleam b/src/content/chapter5_advanced_features/lesson00_use/code.gleam
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+++ b/src/content/chapter5_advanced_features/lesson00_use/code.gleam
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+import gleam/io
+import gleam/result
+
+pub fn main() {
+  io.debug(without_use())
+  io.debug(with_use())
+}
+
+pub fn without_use() {
+  result.try(get_usename(), 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_usename())
+  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_usename() {
+  Ok("alice")
+}
+
+fn get_password() {
+  Ok("hunter2")
+}
+
+fn log_in(_username: String, _password: String) {
+  Ok("Welcome")
+}
diff --git a/src/content/chapter5_advanced_features/lesson00_use/text.html b/src/content/chapter5_advanced_features/lesson00_use/text.html
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+<p>
+  Gleam lacks exceptions, macros, type classes, early returns, and a variety of
+  other features, instead going all-in with just first-class-functions and
+  pattern matching. This makes Gleam code easier to understand, but it can
+  sometimes result in excessive indentation.
+</p>
+<p>
+  Gleam's use expression helps out here by enabling us to write code that uses
+  callbacks in an unindented style, as shown in the code window.
+</p>
+
+<p>
+  The higher order function being called goes on the right hand side of the
+  <code>&lt;-</code> operator. It must take a callback function as its final
+  argument.
+</p>
+<p>
+  The argument names for the callback function go on the left hand side of the
+  <code>&lt;-</code> operator. The function can take any number of arguments,
+  including zero.
+</p>
+<p>
+  All the following code in the <code class="hljs">{}</code> block becomes the
+  body of the callback function.
+</p>
+<p>
+  This is a very capable and useful feature, but excessive application of
+  <code>use</code> may result in code that is unclear otherwise, especially to
+  beginners. Often using the regular function call syntax will result in more
+  approachable code!
+</p>