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Add float.modulo #582

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merged 3 commits into from Jul 17, 2024
Merged

Add float.modulo #582

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003abcb
Add float.modulo
May 9, 2024
0d69e34
Test fractional numbers for float.modulo
May 12, 2024
3560e29
Fix float_test with float.loosely_equals
Jul 12, 2024
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49 changes: 49 additions & 0 deletions src/gleam/float.gleam
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Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,55 @@ fn do_product(numbers: List(Float), initial: Float) -> Float {
@external(javascript, "../gleam_stdlib.mjs", "random_uniform")
pub fn random() -> Float

/// Computes the modulo of an float division of inputs as a `Result`.
///
/// Returns division of the inputs as a `Result`: If the given divisor equals
/// `0`, this function returns an `Error`.
///
/// ## Examples
///
/// ```gleam
/// modulo(3.0, 2.0)
/// // -> Ok(1.0)
/// ```
///
/// ```gleam
/// modulo(1.0, 0.0)
/// // -> Error(Nil)
/// ```
///
/// ```gleam
/// modulo(10.0, -1.0)
/// // -> Ok(0.0)
/// ```
///
/// ```gleam
/// modulo(13.0, by: 3.0)
/// // -> Ok(1.0)
/// ```
///
/// ```gleam
/// modulo(-13.0, by: 3.0)
/// // -> Ok(2.0)
/// ```
///
/// ```gleam
/// modulo(13.0, by: -3.0)
/// // -> Ok(-2.0)
/// ```
///
/// ```gleam
/// modulo(-13.0, by: -3.0)
/// // -> Ok(-1.0)
/// ```
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Can we have fewer examples please? It's a little overwhelming I think

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The comments were copied from the int.modulo function, they explain all the possible behaviours.

  • When divisor is non-zero and when it is zero.
  • That the modulo follows the sign of the divisor.

Can we keep the examples?

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There is too much information here, please reduce it. The examples section is not suitable for an exhaustive description of the behaviour.

///
pub fn modulo(dividend: Float, by divisor: Float) -> Result(Float, Nil) {
case divisor {
0.0 -> Error(Nil)
_ -> Ok(dividend -. floor(dividend /. divisor) *. divisor)
}
}

/// Returns division of the inputs as a `Result`.
///
/// ## Examples
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23 changes: 23 additions & 0 deletions test/gleam/float_test.gleam
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Expand Up @@ -371,6 +371,29 @@ pub fn random_test() {
|> should.be_true
}

pub fn modulo_test() {
float.modulo(3.0, 2.0)
|> should.equal(Ok(1.0))

float.modulo(1.0, 0.0)
|> should.equal(Error(Nil))

float.modulo(10.0, -1.0)
|> should.equal(Ok(0.0))

float.modulo(13.0, by: 3.0)
|> should.equal(Ok(1.0))

float.modulo(-13.0, by: 3.0)
|> should.equal(Ok(2.0))

float.modulo(13.0, by: -3.0)
|> should.equal(Ok(-2.0))

float.modulo(-13.0, by: -3.0)
|> should.equal(Ok(-1.0))
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All of these are whole numbers. Let's have tests for other numbers too.

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Done, could you help me solve this failing test?

Failures:

  1) gleam/float_test.modulo_test
     Values were not equal
     expected: Ok(1.3)
          got: Ok(1.3000000000000007)

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Check https://hexdocs.pm/gleam_stdlib/gleam/float.html#loosely_equals maybe

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Check https://hexdocs.pm/gleam_stdlib/gleam/float.html#loosely_equals maybe

But then I believe I would need to import the result library to unwrap the value before, right? Is it ok adding this dependency?

}

pub fn divide_test() {
float.divide(1.0, 1.0)
|> should.equal(Ok(1.0))
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