use match instead of if-else

Author: majcn

src/majcn/math.rs

@@ -4,116 +4,42 @@ pub trait DigitCounter {
 
 impl DigitCounter for u32 {
     fn count_digits(self) -> usize {
-        if self < 10 {
-            return 1;
+        match self {
+            0..10 => 1,
+            10..100 => 2,
+            100..1000 => 3,
+            1000..10000 => 4,
+            10000..100000 => 5,
+            100000..1000000 => 6,
+            1000000..10000000 => 7,
+            10000000..100000000 => 8,
+            _ => 9,
         }
-
-        if self < 100 {
-            return 2;
-        }
-
-        if self < 1000 {
-            return 3;
-        }
-
-        if self < 10000 {
-            return 4;
-        }
-
-        if self < 100000 {
-            return 5;
-        }
-
-        if self < 1000000 {
-            return 6;
-        }
-
-        if self < 10000000 {
-            return 7;
-        }
-
-        if self < 100000000 {
-            return 8;
-        }
-
-        9
     }
 }
 
 impl DigitCounter for u64 {
     fn count_digits(self) -> usize {
-        if self < 10 {
-            return 1;
-        }
-
-        if self < 100 {
-            return 2;
-        }
-
-        if self < 1000 {
-            return 3;
-        }
-
-        if self < 10000 {
-            return 4;
-        }
-
-        if self < 100000 {
-            return 5;
-        }
-
-        if self < 1000000 {
-            return 6;
+        match self {
+            0..10 => 1,
+            10..100 => 2,
+            100..1000 => 3,
+            1000..10000 => 4,
+            10000..100000 => 5,
+            100000..1000000 => 6,
+            1000000..10000000 => 7,
+            10000000..100000000 => 8,
+            100000000..1000000000 => 9,
+            1000000000..10000000000 => 10,
+            10000000000..100000000000 => 11,
+            100000000000..1000000000000 => 12,
+            1000000000000..10000000000000 => 13,
+            10000000000000..100000000000000 => 14,
+            100000000000000..1000000000000000 => 15,
+            1000000000000000..10000000000000000 => 16,
+            10000000000000000..100000000000000000 => 17,
+            100000000000000000..1000000000000000000 => 18,
+            _ => 19,
         }
-
-        if self < 10000000 {
-            return 7;
-        }
-
-        if self < 100000000 {
-            return 8;
-        }
-
-        if self < 1000000000 {
-            return 9;
-        }
-
-        if self < 10000000000 {
-            return 10;
-        }
-
-        if self < 100000000000 {
-            return 11;
-        }
-
-        if self < 1000000000000 {
-            return 12;
-        }
-
-        if self < 10000000000000 {
-            return 13;
-        }
-
-        if self < 100000000000000 {
-            return 14;
-        }
-
-        if self < 1000000000000000 {
-            return 15;
-        }
-
-        if self < 10000000000000000 {
-            return 16;
-        }
-
-        if self < 100000000000000000 {
-            return 17;
-        }
-
-        if self < 1000000000000000000 {
-            return 18;
-        }
-
-        19
     }
 }