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-rw-r--r--src/content/chapter5_advance_features/lesson01_use_continued/code.gleam30
-rw-r--r--src/content/chapter5_advance_features/lesson01_use_continued/text.html30
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diff --git a/src/content/chapter5_advance_features/lesson01_use_continued/code.gleam b/src/content/chapter5_advance_features/lesson01_use_continued/code.gleam
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+import gleam/io
+import gleam/result
+
+pub fn main() {
+ let x = {
+ use username <- result.try(get_usename())
+ use password <- result.try(get_password())
+ use greeting <- result.map(log_in(username, password))
+ greeting <> ", " <> username
+ }
+
+ case x {
+ Ok(greeting) -> io.println(greeting)
+ Error(error) -> io.println_error(error)
+ }
+}
+
+// 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_advance_features/lesson01_use_continued/text.html b/src/content/chapter5_advance_features/lesson01_use_continued/text.html
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+<p>
+ The <code>use</code> expression is syntactic sugar for a regular function call
+ and an anonymous function.
+</p>
+
+<p>This code:</p>
+<pre>
+use a, b <- my_function
+next(a)
+next(b)
+</pre>
+
+<p>Expands into this code:</p>
+<pre>
+my_function(fn(a, b) {
+ next(a)
+ next(b)
+})
+</pre>
+
+<p>
+ To ensure that your <code>use</code> code works and is as understandable as
+ possible, the right-hand-side ideally should be a function call rather than a
+ pipeline or other expression, which is typically more difficult to read.
+</p>
+
+<p>
+ <code>use</code> is an expression like everything else in Gleam, so it can be
+ placed within blocks.
+</p>