src/lmathlib.js: Implement math.atan second argument

1 files changed, 3 insertions, 1 deletions

diff --git a/src/lmathlib.js b/src/lmathlib.js
index b10f7bf..32893a6 100644
--- a/src/lmathlib.js
+++ b/src/lmathlib.js
@@ -80,7 +80,9 @@ const math_acos = function(L) {
 };
 
 const math_atan = function(L) {
-    lua.lua_pushnumber(L, Math.atan(lauxlib.luaL_checknumber(L, 1)));
+    let y = lauxlib.luaL_checknumber(L, 1);
+    let x = lauxlib.luaL_optnumber(L, 2, 1);
+    lua.lua_pushnumber(L, Math.atan2(y, x));
     return 1;
 };