Add chapters

1 files changed, 19 insertions, 0 deletions

diff --git a/src/content/chapter1_functions/lesson04_generic_functions/code.gleam b/src/content/chapter1_functions/lesson04_generic_functions/code.gleam
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--- /dev/null
+++ b/src/content/chapter1_functions/lesson04_generic_functions/code.gleam
@@ -0,0 +1,19 @@
+import gleam/io
+
+pub fn main() {
+  let add_one = fn(x) { x + 1 }
+  let exclaim = fn(x) { x <> "!" }
+
+  // Invalid, Int and String are not the same type
+  // twice(10, exclaim)
+
+  // Here the type variable is replaced by the type Int
+  io.debug(twice(10, add_one))
+
+  // Here the type variable is replaced by the type String
+  io.debug(twice("Hello", exclaim))
+}
+
+fn twice(argument: value, function: fn(value) -> value) -> value {
+  function(function(argument))
+}