3 files changed, 30 insertions, 24 deletions

diff --git a/src/gleam/float.gleam b/src/gleam/float.gleam
index 1b8220b..d41bc21 100644
--- a/src/gleam/float.gleam
+++ b/src/gleam/float.gleam
@@ -338,22 +338,19 @@ if erlang {
 }
 
 if javascript {
-  /// With round-to-nearest-even behavior, the ranges claimed for the functions below
-  /// (excluding the one for Math.random() itself) aren't exact.
-  /// If extremely large bounds are chosen (2^53 or higher),
-  /// it's possible in extremely rare cases to calculate the usually-excluded upper bound.
-  /// Note that as numbers in JavaScript are IEEE 754 floating point numbers
-  /// See: <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random>
-  ///
   external fn do_random_uniform() -> Float =
     "../gleam_stdlib.mjs" "random_uniform"
 }
 
 pub fn random_between(min: Float, max: Float) -> Float {
   // ```javascript
-  // return Math.floor(Math.random() * (max - min + 1) + min); // The maximum is/should-be exclusive
+  // return Math.random() * (max - min) + min; // The minimum is inclusive and the maximum is exclusive
   // ```
   // See: <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random#getting_a_random_number_between_two_values>
   //
   random_uniform() *. { max -. min } +. min
 }
+
+pub fn random_below(max: Float) -> Float {
+  random_uniform() *. max
+}
diff --git a/src/gleam/int.gleam b/src/gleam/int.gleam
index c255dd0..06ad12c 100644
--- a/src/gleam/int.gleam
+++ b/src/gleam/int.gleam
@@ -1,5 +1,4 @@
 import gleam/order.{Order}
-// import gleam/float.{floor, parse, random}
 import gleam/float
 
 /// Returns the absolute value of the input.
@@ -383,26 +382,25 @@ fn do_undigits(
   }
 }
 
-pub fn random_below(max: Int) -> Int {
-  // ```javascript
-  // return Math.floor(rand * max);
-  // ```
-  // See: <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random>
-  float.random_uniform() *. to_float(max)
-  |> float.floor()
-  |> float.round()
-  // TODO: Does `float.round() `affect random distribution uniformity?
-}
-
 pub fn random_between(min: Int, max: Int) -> Int {
   // ```javascript
   // min = Math.ceil(min);
   // max = Math.floor(max);
-  // return Math.floor(Math.random() * (max - min + 1) + min); //The maximum is inclusive and the minimum is inclusive
+  // return Math.floor(Math.random() * (max - min) + min); // The minimum is inclusive and the maximum is exclusive
   // ```
   // See: <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random#getting_a_random_integer_between_two_values>
-  float.random_between(to_float(min), to_float(max))
+  let min =
+    to_float(min)
+    |> float.ceiling()
+  let max =
+    to_float(max)
+    |> float.floor()
+
+  float.random_between(min, max)
   |> float.floor()
   |> float.round()
-  // TODO: Does float.round() affect random distribution uniformity?
+}
+
+pub fn random_below(max: Int) -> Int {
+  random_between(0, max)
 }
diff --git a/src/gleam_stdlib.mjs b/src/gleam_stdlib.mjs
index 59077e9..6604bff 100644
--- a/src/gleam_stdlib.mjs
+++ b/src/gleam_stdlib.mjs
@@ -247,7 +247,18 @@ export function power(base, exponent) {
 }
 
 export function random_uniform() {
-  return Math.random();
+	let random_uniform_result = Math.random();
+	// With round-to-nearest-even behavior, the ranges claimed for the functions below
+  // (excluding the one for Math.random() itself) aren't exact.
+  // If extremely large bounds are chosen (2^53 or higher),
+  // it's possible in extremely rare cases to calculate the usually-excluded upper bound.
+  // Note that as numbers in JavaScript are IEEE 754 floating point numbers
+  // See: <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random>
+	// Because of this, we just loop 'until' we get a valid result where 0.0 <= x < 1.0:
+	if (random_uniform_result === 1.0) {
+		return random_uniform();
+	}
+  return random_uniform_result;
 }
 
 export function bit_string_slice(bits, position, length) {