Functions

2 files changed, 27 insertions, 0 deletions

diff --git a/lessons/src/lesson013_functions/code.gleam b/lessons/src/lesson013_functions/code.gleam
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+++ b/lessons/src/lesson013_functions/code.gleam
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+import gleam/io
+
+pub fn main() {
+  io.debug(double(10))
+}
+
+fn double(a: Int) -> Int {
+  multiply(a, 2)
+}
+
+fn multiply(a: Int, b: Int) -> Int {
+  a * b
+}
diff --git a/lessons/src/lesson013_functions/text.html b/lessons/src/lesson013_functions/text.html
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+<p>
+  The <code>fn</code> keyword is used to define new functions.
+</p>
+<p>
+  The <code>double</code> and <code>multiply</code> functions are defined
+  without the <code>pub</code> keyword. This makes them <em>private</em>
+  functions, they can only be used within this module. If another module
+  attempted to use them it would result in a compiler error.
+</p>
+<p>
+  Like with assignments, type annotations are optional for function arguments
+  and return values. It is considered good practice to use type annotations for
+  functions, for clarity and to encourage intentional and thoughtful design.
+</p>