[Issue 18728] New: std.math.fdim does not handle nan correctly

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18728

          Issue ID: 18728
           Summary: std.math.fdim does not handle nan correctly
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: jack at jackstouffer.com

assert(fdim(real.nan, 2.0) == 0);

According to the C spec "If either argument is NaN, NaN is returned"

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