First power of 2 that has leading decimal digits of 12: Difference between revisions

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@@ Line 671: / Line 671: @@
 p l n = ([-1 ..] >>= f) !! pred n
   where
-    digitCount = floor $ logBase 10 (fromIntegral l :: Float)
+    digitCount =
+      floor $
+        logBase 10 (fromIntegral l :: Float)
     log10pwr = logBase 10 2
-    f raised =
+    f raised = [ds | l == ds]
-      [ ds
-      | ds == l ]
       where
         ds =
           floor $
-**
+              ** ( snd
-          (snd (properFraction $ log10pwr * realToFrac raised) + realToFrac digitCount)
+                     ( properFraction $
+                         log10pwr * realToFrac raised
+                     )
+                     + realToFrac digitCount
+                 )
 main :: IO ()
@@ Line 686: / Line 691: @@
   mapM_
     (\(l, n) -> printf "p(%d, %d) = %d\n" l n (p l n))
+    [ (12, 1),
-    [(12, 1), (12, 2), (123, 45), (123, 12345), (123, 678910)]</lang>
+      (12, 2),
+      (123, 45),
+      (123, 12345),
+      (123, 678910)
+    ]</lang>
 {{out}}