Add atanh to Math

src/js.rs

@@ -286,6 +286,14 @@ extern {
     #[wasm_bindgen(static_method_of = Math)]
     pub fn atan2(y: i32, x: i32) -> Number;
 
+    /// The Math.atanh() function returns the hyperbolic arctangent of a number,
+    /// that is ∀x ∊ (-1,1), Math.atanh(x) = arctanh(x) = the unique y such that
+    /// tanh(y) = x
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/atanh
+    #[wasm_bindgen(static_method_of = Math)]
+    pub fn atanh(x: i32) -> Number;
+
 }
 
 // Number.

tests/all/js_globals/Math.rs

@@ -186,3 +186,29 @@ fn atan2() {
         "#)
         .test()
 }
+
+#[test]
+fn atanh() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn atanh(x: i32) -> js::Number {
+                js::Math::atanh(x)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                assert.equal(wasm.atanh(1), Math.atanh(1));
+            }
+        "#)
+        .test()
+}