fix: use SQL param order for ATAN2

Author: michaelmior

specs/query-language.md

@@ -144,7 +144,7 @@ Each parameter can be either a constant, field name, or a JSONPath expression.
 - `SQRT(x)`: Returns the square root of `x`
 
 ##### Binary Functions
-- `ATAN2(x, y)`: Returns the arc tangent of `y/x` in radians
+- `ATAN2(y, x)`: Returns the arc tangent of `y/x` in radians
 - `DIV(x, y)`: Returns the integer quotient of `x/y`
 - `LOG(x, y)`: Returns the logarithm of `x` with base `y` (`y` is optional and defaults to e)
 - `LOG10(x)`: Returns the base-10 logarithm of `x`

src/expression.rs

@@ -307,7 +307,7 @@ fn evaluate_function(func: &ScalarFunction, vals: &[Value]) -> Value {
                 None
             };
             match (f1, f2) {
-                (Some(x), Some(y)) => Some(y.atan2(x)),
+                (Some(y), Some(x)) => Some(y.atan2(x)),
                 _ => None,
             }
         }
@@ -569,13 +569,19 @@ mod tests {
         );
 
         // ATAN2(1, 1) -> pi/4
-        // ATAN2(x, y) = atan(y/x).
+        // ATAN2(y, x) = atan(y/x).
         // args: [one, one]. atan(1/1) = atan(1) = pi/4
         let atan2_val = eval_args(ScalarFunction::Atan2, vec!["one", "one"])
             .as_f64()
             .unwrap();
         assert!((atan2_val - std::f64::consts::FRAC_PI_4).abs() < 1e-10);
 
+        // ATAN2(1, 0) -> pi/2 (Y=1, X=0)
+        let atan2_val_2 = eval_args(ScalarFunction::Atan2, vec!["one", "zero"])
+            .as_f64()
+            .unwrap();
+        assert!((atan2_val_2 - std::f64::consts::FRAC_PI_2).abs() < 1e-10);
+
         // ROUND
         // ROUND(0.5) -> 1.0
         assert_eq!(