diff options
| -rw-r--r-- | src/gleam/float.gleam | 27 | ||||
| -rw-r--r-- | test/gleam/float_test.gleam | 10 |
2 files changed, 37 insertions, 0 deletions
diff --git a/src/gleam/float.gleam b/src/gleam/float.gleam index 2e24f0b..385d9b4 100644 --- a/src/gleam/float.gleam +++ b/src/gleam/float.gleam @@ -320,3 +320,30 @@ fn do_product(numbers: List(Float), initial: Float) -> Float { [x, ..rest] -> do_product(rest, x *. initial) } } + +/// Returns a random seed where 0.0 =< random_seed < 1.0 +/// +pub fn random_seed() -> Float { + do_random_seed() +} + +if erlang { + // 0.0 =< X < 1.0 and updates the state in the process dictionary. + /// Returns a random float uniformly distributed in the value range + /// See: <https://www.erlang.org/doc/man/rand.html#uniform-0> + /// + external fn do_random_seed() -> Float = + "rand" "uniform" +} + +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_seed() -> Float = + "math" "random" +} diff --git a/test/gleam/float_test.gleam b/test/gleam/float_test.gleam index 287dc4b..109f728 100644 --- a/test/gleam/float_test.gleam +++ b/test/gleam/float_test.gleam @@ -300,3 +300,13 @@ pub fn product_test() { float.product([2.5, 3.2, 4.2]) |> should.equal(33.6) } + +pub fn random_seed_test() { + let random_seed = float.random_seed() + + { random_seed >=. 0.0 } + |> should.be_true + + { random_seed <. 1.0 } + |> should.be_true +} |