Add math.atan2 (#819)

pkl-core/src/main/java/org/pkl/core/stdlib/math/MathNodes.java

@@ -299,6 +299,28 @@ public final class MathNodes {
     }
   }
 
+  public abstract static class atan2 extends ExternalMethod2Node {
+    @Specialization
+    protected double eval(VmTyped self, long x, long y) {
+      return StrictMath.atan2(x, y);
+    }
+
+    @Specialization
+    protected double eval(VmTyped self, long x, double y) {
+      return StrictMath.atan2(x, y);
+    }
+
+    @Specialization
+    protected double eval(VmTyped self, double x, double y) {
+      return StrictMath.atan2(x, y);
+    }
+
+    @Specialization
+    protected double eval(VmTyped self, double x, long y) {
+      return StrictMath.atan2(x, y);
+    }
+  }
+
   public abstract static class gcd extends ExternalMethod2Node {
     @TruffleBoundary
     @Specialization

pkl-core/src/test/files/LanguageSnippetTests/input/api/mathModule.pkl

@@ -130,6 +130,13 @@ examples {
     math.atan(math.tan(-2.34))
   }
 
+  ["atan2"] {
+    math.atan2(4, -3)
+    math.atan2(4.5, -3.5)
+    math.atan2(4.5, -3)
+    math.atan2(4, 3.5)
+  }
+
   ["gcd"] {
     math.gcd(0, 0)
     math.gcd(4, 6)
@@ -189,3 +196,10 @@ examples {
     math.min(Infinity, -Infinity)
   }
 }
+
+facts {
+  ["atan2"] {
+    math.atan2(1, 0) == math.pi / 2
+    math.atan2(0, -1) == math.pi
+  }
+}

pkl-core/src/test/files/LanguageSnippetTests/output/api/mathModule.pcf

@@ -1,3 +1,9 @@
+facts {
+  ["atan2"] {
+    true
+    true
+  }
+}
 examples {
   ["minInt"] {
     -9223372036854775808
@@ -109,6 +115,12 @@ examples {
     1.1415926535897931
     0.8015926535897934
   }
+  ["atan2"] {
+    2.214297435588181
+    2.2318394956455836
+    2.1587989303424644
+    0.851966327173272
+  }
   ["gcd"] {
     0
     2

stdlib/math.pkl

@@ -145,6 +145,12 @@ external function acos(x: Number): Float
 /// [1]: https://en.wikipedia.org/wiki/Inverse_trigonometric_functions
 external function atan(x: Number): Float
 
+/// Returns the [2-argument arctangent][1] of [x] and [y].
+///
+/// [1]: https://en.wikipedia.org/wiki/Atan2
+@Since { version = "0.28.0" }
+external function atan2(x: Number, y: Number): Float
+
 /// Returns the [greatest common divisor][1] of [x] and [y].
 ///
 /// [1]: https://en.wikipedia.org/wiki/Greatest_common_divisor