Introduce a new chapter on label shorthand syntax

.gitignore

@@ -4,3 +4,4 @@ build
 erl_crash.dump
 /public
 /wasm-compiler
+.DS_Store

src/content/chapter1_functions/lesson08_labelled_arguments/code.gleam

@@ -9,17 +9,6 @@ pub fn main() {
 
   // Using the labels in a different order
   io.debug(calculate(1, multiply: 3, add: 2))
-
-  // You may have some local variables declared
-  let multiply = 3
-  let add = 2
-
-  // You can specify the variables by name when calling the function
-  io.debug(calculate(1, add: add, multiply: multiply))
-
-  // Or use shorthand syntax, if the variable names match the names of the
-  // labelled arguments
-  io.debug(calculate(1, add:, multiply:))
 }
 
 fn calculate(value: Int, add addend: Int, multiply multiplier: Int) {

src/content/chapter1_functions/lesson08_labelled_arguments/en.html

@@ -19,8 +19,3 @@
   Labels are optional when calling a function, it is up to the programmer to
   decide what is clearest in their code.
 </p>
-<p>
-  Additionally, when local variables have the same name as the labelled
-  argument, the variable name can be omitted when calling the function. This is
-  known as shorthand syntax for labels.
-</p>

src/content/chapter1_functions/lesson09_label_shorthand_syntax/code.gleam

@@ -0,0 +1,28 @@
+pub fn main() {
+  let quantity = 5.0
+  let unit_price = 10.0
+  let discount = 0.2
+
+  // Explicitly providing local variable names when calling the function.
+  calculate_total_cost(
+    quantity: quantity,
+    unit_price: unit_price,
+    discount: discount,
+  )
+
+  // However, since our local variable names are identical to the argument
+  // labels, we can omit the variable names entirely and use shorthand label
+  // syntax.
+  calculate_total_cost(quantity:, unit_price:, discount:)
+}
+
+fn calculate_total_cost(
+  quantity quantity: Float,
+  unit_price price: Float,
+  discount discount: Float,
+) -> Float {
+  let subtotal = quantity *. price
+  let discount = subtotal *. discount
+
+  subtotal -. discount
+}

src/content/chapter1_functions/lesson09_label_shorthand_syntax/en.html

@@ -0,0 +1,5 @@
+<p>
+  When local variables have the same names as a function's labelled arguments,
+  the variable names can be omitted when calling the function. This is known as
+  shorthand syntax for labels.
+</p>