add negate functions to int and float modules

5 files changed, 45 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e567952..e920741 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
 - The `list` module gains the `each`, and `partition` functions.
+- The `int` and `float` modules gain the `negate` function.
 
 ## v0.11.0 - 2020-08-22
 
diff --git a/src/gleam/float.gleam b/src/gleam/float.gleam
index ecb203c..24f0330 100644
--- a/src/gleam/float.gleam
+++ b/src/gleam/float.gleam
@@ -160,3 +160,14 @@ pub fn square_root(number: Float) -> Result(Float, Nil) {
     False -> Ok(power(number, 0.5))
   }
 }
+
+/// Returns the negative of the value provided
+///
+/// ## Examples
+///
+///    > negate(1.)
+///    -1.
+///
+pub fn negate(x: Float) -> Float {
+  -1. *. x
+}
diff --git a/src/gleam/int.gleam b/src/gleam/int.gleam
index 151bfa3..2dc4f46 100644
--- a/src/gleam/int.gleam
+++ b/src/gleam/int.gleam
@@ -121,3 +121,14 @@ pub fn is_even(x: Int) -> Bool {
 pub fn is_odd(x: Int) -> Bool {
   x % 2 != 0
 }
+
+/// Returns the negative of the value provided
+///
+/// ## Examples
+///
+///    > negate(1)
+///    -1
+///
+pub fn negate(x: Int) -> Int {
+  -1 * x
+}
diff --git a/test/gleam/float_test.gleam b/test/gleam/float_test.gleam
index 79bece2..be1f22d 100644
--- a/test/gleam/float_test.gleam
+++ b/test/gleam/float_test.gleam
@@ -231,3 +231,14 @@ pub fn square_root_test() {
   float.square_root(-4.0)
   |> should.equal(Error(Nil))
 }
+
+pub fn negate_test() {
+  float.negate(-1.)
+  |> should.equal(1.)
+
+  float.negate(2.)
+  |> should.equal(-2.)
+
+  float.negate(0.)
+  |> should.equal(0.)
+}
diff --git a/test/gleam/int_test.gleam b/test/gleam/int_test.gleam
index bb4648e..4a01073 100644
--- a/test/gleam/int_test.gleam
+++ b/test/gleam/int_test.gleam
@@ -157,3 +157,14 @@ pub fn is_odd_test() {
   int.is_odd(10005)
   |> should.be_true
 }
+
+pub fn negate_test() {
+  int.negate(-1)
+  |> should.equal(1)
+
+  int.negate(2)
+  |> should.equal(-2)
+
+  int.negate(0)
+  |> should.equal(0)
+}