fix factor of 5

Author: peterkrack

pineappl/src/interpolation.rs

@@ -16,7 +16,7 @@ mod applgrid {
     }
 
     pub fn fx2(y: f64) -> f64 {
-        let z = -5.0 * (-y).exp();
+        let z = -5.0 * (5-y).exp();
         let w = lambert_w::lambert_w0(z);
         return -w / 5.0;
     }