Improve the distribution of scaleLinear (#405)

* Improve the distribution of scaleLinear * Style nits (STYLE_GUIDE.md) Co-authored-by: Nikos Baxevanis <[email protected]>
hedgehogqa · Oct 8, 2020 · 06eb474 · moodmosaic · May 25, 2024 · 06eb474
1 parent 0371468
commit 06eb474
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/hedgehog/src/Hedgehog/Internal/Range.hs b/hedgehog/src/Hedgehog/Internal/Range.hs
@@ -305,8 +305,14 @@ scaleLinear sz0 z0 n0 =
     n =
       toInteger n0
 
+    -- @rng@ has magnitude 1 bigger than the biggest diff
+    -- i.e. it specifies the range the diff can be in [0,rng)
+    -- with the upper bound being exclusive.
+    rng =
+      n - z + signum (n - z)
+
     diff =
-      ((n - z) * fromIntegral sz) `quot` 99
+      (rng * fromIntegral sz) `quot` 100
   in
     fromInteger $ z + diff