[Issue 13369] New: std.math.iLog10

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13369

          Issue ID: 13369
           Summary: std.math.iLog10
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: Phobos
          Assignee: nobody at puremagic.com
          Reporter: bearophile_hugs at eml.cc

I suggest to add to Phobos an overloaded function like this:


uint iLog10(in uint x) pure nothrow @safe @nogc
in {
    assert(x > 0);
} body {
    return (x >= 1_000_000_000) ? 9 :
           (x >=   100_000_000) ? 8 :
           (x >=    10_000_000) ? 7 :
           (x >=     1_000_000) ? 6 :
           (x >=       100_000) ? 5 :
           (x >=        10_000) ? 4 :
           (x >=         1_000) ? 3 :
           (x >=           100) ? 2 :
           (x >=            10) ? 1 : 0;
}

uint iLog10(in ulong x) pure nothrow @safe @nogc
in {
    assert(x > 0);
} body {
    return (x >= 10_000_000_000_000_000_000UL) ? 19 :
           (x >=  1_000_000_000_000_000_000UL) ? 18 :
           (x >=    100_000_000_000_000_000UL) ? 17 :
           (x >=     10_000_000_000_000_000UL) ? 16 :
           (x >=      1_000_000_000_000_000UL) ? 15 :
           (x >=        100_000_000_000_000UL) ? 14 :
           (x >=         10_000_000_000_000UL) ? 13 :
           (x >=          1_000_000_000_000UL) ? 12 :
           (x >=            100_000_000_000UL) ? 11 :
           (x >=             10_000_000_000UL) ? 10 :
           (x >=              1_000_000_000UL) ?  9 :
           (x >=                100_000_000UL) ?  8 :
           (x >=                 10_000_000UL) ?  7 :
           (x >=                  1_000_000UL) ?  6 :
           (x >=                    100_000UL) ?  5 :
           (x >=                     10_000UL) ?  4 :
           (x >=                      1_000UL) ?  3 :
           (x >=                        100UL) ?  2 :
           (x >=                         10UL) ?  1 : 0;
}


See also Issue 9762 .

--