Simplify random

6 files changed, 95 insertions, 154 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d95773a..64d52a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- The `int.random` function now takes a single argument.
+- The `float.random` function no longer takes any arguments.
 - Changed `list.index_map` callback signature to `fn(a, Int) -> b` from
   `fn(Int, a) -> b`, to be consistent with `list.index_fold`.
 - Changed `iterator.index` to return `Iterator(#(a, Int))` instead of
diff --git a/src/gleam/float.gleam b/src/gleam/float.gleam
index 5d62419..e53074d 100644
--- a/src/gleam/float.gleam
+++ b/src/gleam/float.gleam
@@ -416,27 +416,22 @@ fn do_product(numbers: List(Float), initial: Float) -> Float {
   }
 }
 
-/// Generates a random float between the given minimum and maximum values.
+/// Generates a random float between the given zero (inclusive) and one
+/// (exclusive).
 ///
+/// On Erlang this updates the random state in the process dictionary.
+/// See: <https://www.erlang.org/doc/man/rand.html#uniform-0>
 ///
 /// ## Examples
 ///
 /// ```gleam
-/// > random(1.0, 5.0)
-/// 2.646355926896028
+/// > random()
+/// 0.646355926896028
 /// ```
 ///
-pub fn random(min: Float, max: Float) -> Float {
-  do_random_uniform() *. { max -. min } +. min
-}
-
-/// Returns a random float uniformly distributed in the value range
-/// 0.0 =< X < 1.0 and updates the state in the process dictionary.
-/// See: <https://www.erlang.org/doc/man/rand.html#uniform-0>
-///
 @external(erlang, "rand", "uniform")
 @external(javascript, "../gleam_stdlib.mjs", "random_uniform")
-fn do_random_uniform() -> Float
+pub fn random() -> Float
 
 /// Returns division of the inputs as a `Result`.
 ///
diff --git a/src/gleam/int.gleam b/src/gleam/int.gleam
index d93c16a..86c77fa 100644
--- a/src/gleam/int.gleam
+++ b/src/gleam/int.gleam
@@ -526,17 +526,29 @@ fn do_undigits(
   }
 }
 
-/// Generates a random int between the given minimum and maximum values.
+/// Generates a random int between zero and the given maximum.
+///
+/// The lower number is inclusive, the upper number is exclusive.
 ///
 /// ## Examples
 ///
 /// ```gleam
-/// > random(1, 5)
-/// 2
+/// > random(10)
+/// 4
+/// ```
+///
+/// ```gleam
+/// > random(1)
+/// 0
+/// ```
+///
+/// ```gleam
+/// > random(-1)
+/// -1
 /// ```
 ///
-pub fn random(min: Int, max: Int) -> Int {
-  float.random(to_float(min), to_float(max))
+pub fn random(max: Int) -> Int {
+  { float.random() *. to_float(max) }
   |> float.floor()
   |> float.round()
 }
diff --git a/src/gleam/list.gleam b/src/gleam/list.gleam
index 5f62e58..f8ede18 100644
--- a/src/gleam/list.gleam
+++ b/src/gleam/list.gleam
@@ -428,15 +428,11 @@ pub fn map_fold(
   from acc: acc,
   with fun: fn(acc, a) -> #(acc, b),
 ) -> #(acc, List(b)) {
-  fold(
-    over: list,
-    from: #(acc, []),
-    with: fn(acc, item) {
-      let #(current_acc, items) = acc
-      let #(next_acc, next_item) = fun(current_acc, item)
-      #(next_acc, [next_item, ..items])
-    },
-  )
+  fold(over: list, from: #(acc, []), with: fn(acc, item) {
+    let #(current_acc, items) = acc
+    let #(next_acc, next_item) = fun(current_acc, item)
+    #(next_acc, [next_item, ..items])
+  })
   |> pair.map_second(reverse)
 }
 
@@ -1438,16 +1434,13 @@ pub fn key_find(
   in keyword_list: List(#(k, v)),
   find desired_key: k,
 ) -> Result(v, Nil) {
-  find_map(
-    keyword_list,
-    fn(keyword) {
-      let #(key, value) = keyword
-      case key == desired_key {
-        True -> Ok(value)
-        False -> Error(Nil)
-      }
-    },
-  )
+  find_map(keyword_list, fn(keyword) {
+    let #(key, value) = keyword
+    case key == desired_key {
+      True -> Ok(value)
+      False -> Error(Nil)
+    }
+  })
 }
 
 /// Given a list of 2-element tuples, finds all tuples that have a given
@@ -1472,16 +1465,13 @@ pub fn key_filter(
   in keyword_list: List(#(k, v)),
   find desired_key: k,
 ) -> List(v) {
-  filter_map(
-    keyword_list,
-    fn(keyword) {
-      let #(key, value) = keyword
-      case key == desired_key {
-        True -> Ok(value)
-        False -> Error(Nil)
-      }
-    },
-  )
+  filter_map(keyword_list, fn(keyword) {
+    let #(key, value) = keyword
+    case key == desired_key {
+      True -> Ok(value)
+      False -> Error(Nil)
+    }
+  })
 }
 
 fn do_pop(haystack, predicate, checked) {
@@ -1590,16 +1580,13 @@ pub fn key_pop(
   haystack: List(#(k, v)),
   key: k,
 ) -> Result(#(v, List(#(k, v))), Nil) {
-  pop_map(
-    haystack,
-    fn(entry) {
-      let #(k, v) = entry
-      case k {
-        k if k == key -> Ok(v)
-        _ -> Error(Nil)
-      }
-    },
-  )
+  pop_map(haystack, fn(entry) {
+    let #(k, v) = entry
+    case k {
+      k if k == key -> Ok(v)
+      _ -> Error(Nil)
+    }
+  })
 }
 
 /// Given a list of 2-element tuples, inserts a key and value into the list.
@@ -1720,15 +1707,12 @@ pub fn permutations(l: List(a)) -> List(List(a)) {
       l
       |> index_map(fn(i, i_idx) {
         l
-        |> index_fold(
-          [],
-          fn(acc, j, j_idx) {
-            case i_idx == j_idx {
-              True -> acc
-              False -> [j, ..acc]
-            }
-          },
-        )
+        |> index_fold([], fn(acc, j, j_idx) {
+          case i_idx == j_idx {
+            True -> acc
+            False -> [j, ..acc]
+          }
+        })
         |> reverse
         |> permutations
         |> map(fn(permutation) { [i, ..permutation] })
@@ -2030,11 +2014,9 @@ pub fn combinations(items: List(a), by n: Int) -> List(List(a)) {
           let first_combinations =
             map(combinations(xs, n - 1), with: fn(com) { [x, ..com] })
             |> reverse
-          fold(
-            first_combinations,
-            combinations(xs, n),
-            fn(acc, c) { [c, ..acc] },
-          )
+          fold(first_combinations, combinations(xs, n), fn(acc, c) {
+            [c, ..acc]
+          })
         }
       }
   }
@@ -2125,18 +2107,14 @@ fn do_shuffle_pair_unwrap(list: List(#(Float, a)), acc: List(a)) -> List(a) {
 fn do_shuffle_by_pair_indexes(
   list_of_pairs: List(#(Float, a)),
 ) -> List(#(Float, a)) {
-  sort(
-    list_of_pairs,
-    fn(a_pair: #(Float, a), b_pair: #(Float, a)) -> Order {
-      float.compare(a_pair.0, b_pair.0)
-    },
-  )
+  sort(list_of_pairs, fn(a_pair: #(Float, a), b_pair: #(Float, a)) -> Order {
+    float.compare(a_pair.0, b_pair.0)
+  })
 }
 
 /// Takes a list, randomly sorts all items and returns the shuffled list.
 ///
-/// This function uses Erlang's `:rand` module or Javascript's
-/// `Math.random()` to calculate the index shuffling.
+/// This function uses `float.random` to decide the order of the elements.
 ///
 /// ## Example
 ///
@@ -2148,7 +2126,7 @@ fn do_shuffle_by_pair_indexes(
 ///
 pub fn shuffle(list: List(a)) -> List(a) {
   list
-  |> fold(from: [], with: fn(acc, a) { [#(float.random(0.0, 1.0), a), ..acc] })
+  |> fold(from: [], with: fn(acc, a) { [#(float.random(), a), ..acc] })
   |> do_shuffle_by_pair_indexes()
   |> do_shuffle_pair_unwrap([])
 }
diff --git a/test/gleam/float_test.gleam b/test/gleam/float_test.gleam
index e3278d5..4e881f1 100644
--- a/test/gleam/float_test.gleam
+++ b/test/gleam/float_test.gleam
@@ -348,55 +348,27 @@ pub fn product_test() {
 }
 
 pub fn random_test() {
-  let test_boundaries = fn(_accumulator, _element) {
-    float.random(0.0, 0.0)
-    |> should.equal(0.0)
-
-    float.random(0.0, 10.0)
-    |> fn(x) { x >=. 0.0 && x <. 10.0 }
-    |> should.be_true
-
-    float.random(10.0, 0.0)
-    |> fn(x) { x >=. 0.0 && x <. 10.0 }
-    |> should.be_true
-
-    float.random(0.0, -10.0)
-    |> fn(x) { x >=. -10.0 && x <. 0.0 }
-    |> should.be_true
-
-    float.random(-10.0, 0.0)
-    |> fn(x) { x >=. -10.0 && x <. 0.0 }
-    |> should.be_true
-
-    float.random(-10.0, 10.0)
-    |> fn(x) { x >=. -10.0 && x <. 10.0 }
-    |> should.be_true
-
-    float.random(10.0, -10.0)
-    |> fn(x) { x >=. -10.0 && x <. 10.0 }
-    |> should.be_true
-  }
-  list.range(0, 100)
-  |> iterator.from_list()
-  |> iterator.fold(Nil, test_boundaries)
-
-  let test_mean = fn(iterations: Int, min: Float, max: Float, tolerance: Float) {
-    let expected_average = float.sum([min, max]) /. 2.0
+  let expected_average = 0.5
+  let iterations = 10_000
+  let sum =
     list.range(0, iterations)
     |> iterator.from_list()
-    |> iterator.fold(
-      from: 0.0,
-      with: fn(accumulator, _element) { accumulator +. float.random(min, max) },
-    )
-    |> fn(sum) { sum /. int.to_float(iterations) }
-    |> float.loosely_equals(expected_average, tolerance)
-    |> should.be_true
-  }
-  test_mean(100, 0.0, 0.0, 5.0)
-  test_mean(1000, 0.0, 100.0, 5.0)
-  test_mean(1000, -100.0, 100.0, 5.0)
-  test_mean(1000, -100.0, 0.0, 5.0)
-  test_mean(1000, 0.0, -100.0, 5.0)
+    |> iterator.fold(from: 0.0, with: fn(accumulator, _element) {
+      let i = float.random()
+
+      { i <. 1.0 }
+      |> should.be_true
+      { i >=. 0.0 }
+      |> should.be_true
+
+      accumulator +. i
+    })
+  let average = sum /. int.to_float(iterations)
+
+  { average <. expected_average +. 0.1 }
+  |> should.be_true
+  { average >. expected_average -. 0.1 }
+  |> should.be_true
 }
 
 pub fn divide_test() {
diff --git a/test/gleam/int_test.gleam b/test/gleam/int_test.gleam
index b9aac9d..e3ee369 100644
--- a/test/gleam/int_test.gleam
+++ b/test/gleam/int_test.gleam
@@ -394,44 +394,26 @@ pub fn undigits_test() {
 
 pub fn random_test() {
   let test_boundaries = fn(_accumulator, _element) {
-    int.random(0, 0)
+    int.random(0)
     |> should.equal(0)
 
-    int.random(-1, 0)
-    |> list.contains([-1, 0], _)
-    |> should.be_true
+    int.random(1)
+    |> should.equal(0)
+
+    int.random(-1)
+    |> should.equal(-1)
 
-    int.random(-1, 1)
-    |> list.contains([-1, 0], _)
+    int.random(2)
+    |> list.contains([0, 1], _)
     |> should.be_true
 
-    int.random(-1, 2)
-    |> list.contains([-1, 0, 1], _)
+    int.random(3)
+    |> list.contains([0, 1, 2], _)
     |> should.be_true
   }
   list.range(0, 100)
   |> iterator.from_list
   |> iterator.fold(Nil, test_boundaries)
-
-  let test_average = fn(iterations: Int, min: Int, max: Int, tolerance: Int) {
-    let expected_average = int.sum([min, max]) / 2
-    list.range(0, iterations)
-    |> iterator.from_list
-    |> iterator.fold(
-      from: 0,
-      with: fn(accumulator, _element) { accumulator + int.random(min, max) },
-    )
-    |> fn(sum) { sum / iterations }
-    |> fn(average) {
-      average - tolerance <= expected_average || average + tolerance >= expected_average
-    }
-    |> should.be_true
-  }
-  test_average(100, 0, 0, 5)
-  test_average(1000, 0, 100, 5)
-  test_average(1000, -100, 100, 5)
-  test_average(1000, -100, 0, 5)
-  test_average(1000, 0, -100, 5)
 }
 
 pub fn divide_test() {