io.{prinln, debug}

Author: lpil

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## Unreleased
 
 - Created the `set` module with the `new`, `insert`, and `contains` functions.
-- Created the `io` module with the `print` function.
+- Created the `io` module with the `print`, `println`, and `debug` functions.
 - Created the `queue` module with the `new`, `from_list`, `to_list`,
   `is_empty`, `length`, `push_back`, `push_front`, `pop_back`, `pop_front`,
   `reverse`, `is_logically_equal`, and `is_equal` functions.
@@ -18,7 +18,8 @@
   `pop_grapheme` and `to_graphemes' functions.
 - `uri` module created with `parse`, `parse_query`, `path_segments`,
   `query_to_string` and `to_string`.
-- The `dynamic` module gains the `map`, `opaque_list`, `tuple2`, and `tuple2_of` functions.
+- The `dynamic` module gains the `map`, `opaque_list`, `tuple2`, and
+  `tuple2_of` functions.
 - The `list` module gains the `filter_map` function.
 - The `list.contains` label `has` has been changed to `any`.
 

src/gleam/io.gleam

@@ -1,17 +1,57 @@
 external type DoNotLeak
 
-external fn erl_print(String) -> DoNotLeak =
+external fn erl_print(String, List(a)) -> DoNotLeak =
   "io" "fwrite"
 
 /// Writes a string to standard output.
 ///
 /// ## Example
 ///
 ///    > io.print("Hi mum")
+///    // -> Hi mum
 ///    Nil
-///    //=> Hi mum
-///   
+///
 pub fn print(string: String) -> Nil {
-  erl_print(string)
+  erl_print(string, [])
+  Nil
+}
+
+/// Writes a string to standard output, appending a newline to the end.
+///
+/// ## Example
+///
+///    > io.println("Hi mum")
+///    // -> Hi mum
+///    Nil
+///
+pub fn println(string: String) -> Nil {
+  erl_print("~ts\n", [string])
+  Nil
+}
+
+/// Print a value to standard output using Erlang syntax.
+///
+/// The value is returned after being printed so it can be used in pipelines.
+///
+/// ## Example
+///
+///    > io.debug("Hi mum")
+///    // -> <<"Hi mum">>
+///    "Hi mum"
+///
+///    > io.debug(Ok(1))
+///    // -> {ok, 1}
+///    Ok(1)
+///
+///    > import list
+///    > [1, 2]
+///    > |> list.map(fn(x) { x + 1 })
+///    > |> io.debug
+///    > |> list.map(fn(x) { x * 2 })
+///    // -> [2, 3]
+///    [4, 6]
+///
+pub fn debug(term: anything) -> Nil {
+  erl_print("~tp\n", [term])
   Nil
 }