Solve day 1 of 2020 in Gleam

9 files changed, 138 insertions, 0 deletions

diff --git a/aoc-2020-gleam/gleam.toml b/aoc-2020-gleam/gleam.toml
new file mode 100644
index 0000000..cf6aa37
--- /dev/null
+++ b/aoc-2020-gleam/gleam.toml
@@ -0,0 +1,7 @@
+name = "aoc_2020_gleam"
+version = "0.1.0"
+description = "A Gleam project"
+
+[dependencies]
+gleam_stdlib = "~> 0.26"
+gleam_erlang = "~> 0.17"
diff --git a/aoc-2020-gleam/manifest.toml b/aoc-2020-gleam/manifest.toml
new file mode 100644
index 0000000..b1d3141
--- /dev/null
+++ b/aoc-2020-gleam/manifest.toml
@@ -0,0 +1,11 @@
+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "gleam_erlang", version = "0.17.1", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "BAAA84F5BCC4477E809BA3E03BB3009A3894A6544C1511626C44408E39DB2AE6" },
+  { name = "gleam_stdlib", version = "0.26.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "6221F9D7A08B6D6DBCDD567B2BB7C4B2A7BBF4C04C6110757BE04635143BDEC8" },
+]
+
+[requirements]
+gleam_erlang = "~> 0.17"
+gleam_stdlib = "~> 0.26"
diff --git a/aoc-2020-gleam/src/aoc_2020_gleam.gleam b/aoc-2020-gleam/src/aoc_2020_gleam.gleam
new file mode 100644
index 0000000..e27910d
--- /dev/null
+++ b/aoc-2020-gleam/src/aoc_2020_gleam.gleam
@@ -0,0 +1,11 @@
+import gleam/io
+import util/runner
+import days/day01
+
+pub fn main() -> Nil {
+  use day <- runner.with_day()
+  case day {
+    1 -> day01.run()
+    _ -> io.println("Day not found!")
+  }
+}
diff --git a/aoc-2020-gleam/src/days/day01.gleam b/aoc-2020-gleam/src/days/day01.gleam
new file mode 100644
index 0000000..6e75826
--- /dev/null
+++ b/aoc-2020-gleam/src/days/day01.gleam
@@ -0,0 +1,34 @@
+import gleam/io
+import gleam/int
+import gleam/list
+import gleam/result
+import ext/resultx
+import util/input_util
+
+fn solve(numbers: List(Int), n: Int) -> Int {
+  numbers
+  |> list.combinations(by: n)
+  |> list.find(one_that: fn(p) { int.sum(p) == 2020 })
+  |> result.map(with: int.product)
+  |> resultx.force_unwrap()
+}
+
+fn part1(numbers: List(Int)) -> Int {
+  solve(numbers, 2)
+}
+
+fn part2(numbers: List(Int)) -> Int {
+  solve(numbers, 3)
+}
+
+pub fn run() -> Nil {
+  let test = input_util.read_numbers("test01")
+  assert 514_579 = part1(test)
+  assert 241_861_950 = part2(test)
+
+  let input = input_util.read_numbers("day01")
+  io.debug(part1(input))
+  io.debug(part2(input))
+
+  Nil
+}
diff --git a/aoc-2020-gleam/src/ext/intx.gleam b/aoc-2020-gleam/src/ext/intx.gleam
new file mode 100644
index 0000000..3cfe144
--- /dev/null
+++ b/aoc-2020-gleam/src/ext/intx.gleam
@@ -0,0 +1,8 @@
+import gleam/int
+import ext/resultx
+
+pub fn force_parse(string: String) -> Int {
+  string
+  |> int.parse()
+  |> resultx.force_unwrap()
+}
diff --git a/aoc-2020-gleam/src/ext/resultx.gleam b/aoc-2020-gleam/src/ext/resultx.gleam
new file mode 100644
index 0000000..1748d77
--- /dev/null
+++ b/aoc-2020-gleam/src/ext/resultx.gleam
@@ -0,0 +1,4 @@
+pub fn force_unwrap(result: Result(t, _)) -> t {
+  assert Ok(value) = result
+  value
+}
diff --git a/aoc-2020-gleam/src/ext/stringx.gleam b/aoc-2020-gleam/src/ext/stringx.gleam
new file mode 100644
index 0000000..6096465
--- /dev/null
+++ b/aoc-2020-gleam/src/ext/stringx.gleam
@@ -0,0 +1,5 @@
+import gleam/string
+
+pub fn is_not_empty(str: String) -> Bool {
+  !string.is_empty(str)
+}
diff --git a/aoc-2020-gleam/src/util/input_util.gleam b/aoc-2020-gleam/src/util/input_util.gleam
new file mode 100644
index 0000000..3e6b076
--- /dev/null
+++ b/aoc-2020-gleam/src/util/input_util.gleam
@@ -0,0 +1,26 @@
+import gleam/list
+import gleam/string
+import gleam/erlang/file
+import ext/intx
+import ext/stringx
+import ext/resultx
+
+pub fn read_text(filename: String) -> String {
+  "data/" <> filename <> ".txt"
+  |> file.read()
+  |> resultx.force_unwrap()
+}
+
+pub fn read_lines(filename: String) -> List(String) {
+  filename
+  |> read_text()
+  |> string.split(on: "\n")
+  |> list.map(with: string.trim)
+  |> list.filter(for: stringx.is_not_empty)
+}
+
+pub fn read_numbers(filename: String) -> List(Int) {
+  filename
+  |> read_lines()
+  |> list.map(with: intx.force_parse)
+}
diff --git a/aoc-2020-gleam/src/util/runner.gleam b/aoc-2020-gleam/src/util/runner.gleam
new file mode 100644
index 0000000..0ff0a41
--- /dev/null
+++ b/aoc-2020-gleam/src/util/runner.gleam
@@ -0,0 +1,32 @@
+import gleam/list
+import gleam/int
+import gleam/io
+import gleam/result
+import gleam/erlang.{start_arguments}
+
+fn get_day(handler: fn(Int) -> Nil) -> Result(Nil, String) {
+  let args = start_arguments()
+
+  use first <- result.then(
+    args
+    |> list.first()
+    |> result.replace_error("Pass the day as first argument!"),
+  )
+
+  use day <- result.then(
+    first
+    |> int.parse()
+    |> result.replace_error("The day argument must be a number!"),
+  )
+
+  handler(day)
+
+  Ok(Nil)
+}
+
+pub fn with_day(handler: fn(Int) -> Nil) -> Nil {
+  handler
+  |> get_day()
+  |> result.map_error(io.println)
+  |> result.unwrap(Nil)
+}