library/core/tests/num/int_log.rs

   1 //! This tests the `Integer::{ilog,log2,log10}` methods. These tests are in a
   2 //! separate file because there's both a large number of them, and not all tests
   3 //! can be run on Android. This is because in Android `ilog2` uses an imprecise
   4 //! approximation:https://github.com/rust-lang/rust/blob/4825e12fc9c79954aa0fe18f5521efa6c19c7539/src/libstd/sys/unix/android.rs#L27-L53
   5
   6 #[test]
   7 fn checked_ilog() {
   8     assert_eq!(999u32.checked_ilog(10), Some(2));
   9     assert_eq!(1000u32.checked_ilog(10), Some(3));
  10     assert_eq!(555u32.checked_ilog(13), Some(2));
  11     assert_eq!(63u32.checked_ilog(4), Some(2));
  12     assert_eq!(64u32.checked_ilog(4), Some(3));
  13     assert_eq!(10460353203u64.checked_ilog(3), Some(21));
  14     assert_eq!(10460353202u64.checked_ilog(3), Some(20));
  15     assert_eq!(147808829414345923316083210206383297601u128.checked_ilog(3), Some(80));
  16     assert_eq!(147808829414345923316083210206383297600u128.checked_ilog(3), Some(79));
  17     assert_eq!(22528399544939174411840147874772641u128.checked_ilog(19683), Some(8));
  18     assert_eq!(22528399544939174411840147874772631i128.checked_ilog(19683), Some(7));
  19
  20     assert_eq!(0u8.checked_ilog(4), None);
  21     assert_eq!(0u16.checked_ilog(4), None);
  22     assert_eq!(0i8.checked_ilog(4), None);
  23     assert_eq!(0i16.checked_ilog(4), None);
  24
  25     #[cfg(not(miri))] // Miri is too slow
  26     for i in i16::MIN..=0 {
  27         assert_eq!(i.checked_ilog(4), None);
  28     }
  29     #[cfg(not(miri))] // Miri is too slow
  30     for i in 1..=i16::MAX {
  31         assert_eq!(i.checked_ilog(13), Some((i as f32).log(13.0) as u32));
  32     }
  33     #[cfg(not(miri))] // Miri is too slow
  34     for i in 1..=u16::MAX {
  35         assert_eq!(i.checked_ilog(13), Some((i as f32).log(13.0) as u32));
  36     }
  37 }
  38
  39 #[test]
  40 fn checked_ilog2() {
  41     assert_eq!(5u32.checked_ilog2(), Some(2));
  42     assert_eq!(0u64.checked_ilog2(), None);
  43     assert_eq!(128i32.checked_ilog2(), Some(7));
  44     assert_eq!((-55i16).checked_ilog2(), None);
  45
  46     assert_eq!(0u8.checked_ilog2(), None);
  47     assert_eq!(0u16.checked_ilog2(), None);
  48     assert_eq!(0i8.checked_ilog2(), None);
  49     assert_eq!(0i16.checked_ilog2(), None);
  50
  51     for i in 1..=u8::MAX {
  52         assert_eq!(i.checked_ilog2(), Some((i as f32).log2() as u32));
  53     }
  54     #[cfg(not(miri))] // Miri is too slow
  55     for i in 1..=u16::MAX {
  56         // Guard against Android's imprecise f32::ilog2 implementation.
  57         if i != 8192 && i != 32768 {
  58             assert_eq!(i.checked_ilog2(), Some((i as f32).log2() as u32));
  59         }
  60     }
  61     for i in i8::MIN..=0 {
  62         assert_eq!(i.checked_ilog2(), None);
  63     }
  64     for i in 1..=i8::MAX {
  65         assert_eq!(i.checked_ilog2(), Some((i as f32).log2() as u32));
  66     }
  67     #[cfg(not(miri))] // Miri is too slow
  68     for i in i16::MIN..=0 {
  69         assert_eq!(i.checked_ilog2(), None);
  70     }
  71     #[cfg(not(miri))] // Miri is too slow
  72     for i in 1..=i16::MAX {
  73         // Guard against Android's imprecise f32::ilog2 implementation.
  74         if i != 8192 {
  75             assert_eq!(i.checked_ilog2(), Some((i as f32).log2() as u32));
  76         }
  77     }
  78 }
  79
  80 // Validate cases that fail on Android's imprecise float ilog2 implementation.
  81 #[test]
  82 #[cfg(not(target_os = "android"))]
  83 fn checked_ilog2_not_android() {
  84     assert_eq!(8192u16.checked_ilog2(), Some((8192f32).log2() as u32));
  85     assert_eq!(32768u16.checked_ilog2(), Some((32768f32).log2() as u32));
  86     assert_eq!(8192i16.checked_ilog2(), Some((8192f32).log2() as u32));
  87 }
  88
  89 #[test]
  90 fn checked_ilog10() {
  91     assert_eq!(0u8.checked_ilog10(), None);
  92     assert_eq!(0u16.checked_ilog10(), None);
  93     assert_eq!(0i8.checked_ilog10(), None);
  94     assert_eq!(0i16.checked_ilog10(), None);
  95
  96     #[cfg(not(miri))] // Miri is too slow
  97     for i in i16::MIN..=0 {
  98         assert_eq!(i.checked_ilog10(), None);
  99     }
 100     #[cfg(not(miri))] // Miri is too slow
 101     for i in 1..=i16::MAX {
 102         assert_eq!(i.checked_ilog10(), Some((i as f32).log10() as u32));
 103     }
 104     #[cfg(not(miri))] // Miri is too slow
 105     for i in 1..=u16::MAX {
 106         assert_eq!(i.checked_ilog10(), Some((i as f32).log10() as u32));
 107     }
 108     #[cfg(not(miri))] // Miri is too slow
 109     for i in 1..=100_000u32 {
 110         assert_eq!(i.checked_ilog10(), Some((i as f32).log10() as u32));
 111     }
 112 }
 113
 114 macro_rules! ilog10_loop {
 115     ($T:ty, $ilog10_max:expr) => {
 116         assert_eq!(<$T>::MAX.ilog10(), $ilog10_max);
 117         for i in 0..=$ilog10_max {
 118             let p = (10 as $T).pow(i as u32);
 119             if p >= 10 {
 120                 assert_eq!((p - 9).ilog10(), i - 1);
 121                 assert_eq!((p - 1).ilog10(), i - 1);
 122             }
 123             assert_eq!(p.ilog10(), i);
 124             assert_eq!((p + 1).ilog10(), i);
 125             if p >= 10 {
 126                 assert_eq!((p + 9).ilog10(), i);
 127             }
 128
 129             // also check `x.ilog(10)`
 130             if p >= 10 {
 131                 assert_eq!((p - 9).ilog(10), i - 1);
 132                 assert_eq!((p - 1).ilog(10), i - 1);
 133             }
 134             assert_eq!(p.ilog(10), i);
 135             assert_eq!((p + 1).ilog(10), i);
 136             if p >= 10 {
 137                 assert_eq!((p + 9).ilog(10), i);
 138             }
 139         }
 140     };
 141 }
 142
 143 #[test]
 144 fn ilog10_u8() {
 145     ilog10_loop! { u8, 2 }
 146 }
 147
 148 #[test]
 149 fn ilog10_u16() {
 150     ilog10_loop! { u16, 4 }
 151 }
 152
 153 #[test]
 154 fn ilog10_u32() {
 155     ilog10_loop! { u32, 9 }
 156 }
 157
 158 #[test]
 159 fn ilog10_u64() {
 160     ilog10_loop! { u64, 19 }
 161 }
 162
 163 #[test]
 164 fn ilog10_u128() {
 165     ilog10_loop! { u128, 38 }
 166 }