Add function.curryN

3 files changed, 75 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e3c67f7..1956083 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- The `function` module gains `curry2` to `curry6`.
 - The `list` module gains the `each`, and `partition` functions.
 - The `int` and `float` modules gain the `negate` function.
 - The `result` module gains the `all` function.
diff --git a/src/gleam/function.gleam b/src/gleam/function.gleam
index 70da466..08e7efd 100644
--- a/src/gleam/function.gleam
+++ b/src/gleam/function.gleam
@@ -7,6 +7,40 @@ pub fn compose(fun1: fn(a) -> b, fun2: fn(b) -> c) -> fn(a) -> c {
   fn(a) { fun2(fun1(a)) }
 }
 
+/// Takes a function with arity two
+/// and returns a curried equivalent.
+/// fn(a, b) -> c becomes fn(a) -> fn(b) -> c
+pub fn curry2(fun: fn(a, b) -> value) {
+  fn(a) { fn(b) { fun(a, b) } }
+}
+
+/// Takes a function with arity three
+/// and returns a curried equivalent.
+/// fn(a, b, c) -> d becomes fn(a) -> fn(b) -> fn(c) -> d
+pub fn curry3(fun: fn(a, b, c) -> value) {
+  fn(a) { fn(b) { fn(c) { fun(a, b, c) } } }
+}
+
+/// Takes a function with arity four
+/// and returns a curried equivalent.
+pub fn curry4(fun: fn(a, b, c, d) -> value) {
+  fn(a) { fn(b) { fn(c) { fn(d) { fun(a, b, c, d) } } } }
+}
+
+/// Takes a function with arity five
+/// and returns a curried equivalent.
+pub fn curry5(fun: fn(a, b, c, d, e) -> value) {
+  fn(a) { fn(b) { fn(c) { fn(d) { fn(e) { fun(a, b, c, d, e) } } } } }
+}
+
+/// Takes a function with arity six
+/// and returns a curried equivalent.
+pub fn curry6(fun: fn(a, b, c, d, e, f) -> value) {
+  fn(a) {
+    fn(b) { fn(c) { fn(d) { fn(e) { fn(f) { fun(a, b, c, d, e, f) } } } } }
+  }
+}
+
 /// Takes a function that takes two arguments and returns a new function that
 /// takes the same two arguments, but in reverse order.
 ///
diff --git a/test/gleam/function_test.gleam b/test/gleam/function_test.gleam
index 9aca032..c9ef8ad 100644
--- a/test/gleam/function_test.gleam
+++ b/test/gleam/function_test.gleam
@@ -32,6 +32,46 @@ pub fn compose_test() {
   |> should.equal("0")
 }
 
+pub fn curry2_test() {
+  let fun = fn(a, b) { a + b }
+  let curried = function.curry2(fun)
+
+  curried(1)(2)
+  |> should.equal(3)
+}
+
+pub fn curry3_test() {
+  let fun = fn(a, b, c) { a + b + c }
+  let curried = function.curry3(fun)
+
+  curried(1)(2)(4)
+  |> should.equal(7)
+}
+
+pub fn curry4_test() {
+  let fun = fn(a, b, c, d) { a + b + c + d }
+  let curried = function.curry4(fun)
+
+  curried(1)(2)(4)(8)
+  |> should.equal(15)
+}
+
+pub fn curry5_test() {
+  let fun = fn(a, b, c, d, e) { a + b + c + d + e }
+  let curried = function.curry5(fun)
+
+  curried(1)(2)(4)(8)(16)
+  |> should.equal(31)
+}
+
+pub fn curry6_test() {
+  let fun = fn(a, b, c, d, e, f) { a + b + c + d + e + f }
+  let curried = function.curry6(fun)
+
+  curried(1)(2)(4)(8)(16)(32)
+  |> should.equal(63)
+}
+
 pub fn flip_test() {
   let fun = fn(s: String, i: Int) {
     s