c++ - How to compare a long long with a double? -



c++ - How to compare a long long with a double? -

(this has duplicate, can't find duplicate...) how compare long long double in c++?

casting either other can cause loss of precision , perchance overflow, i'm not sure do...

honestly: utilize long double on platform long doubles have 64-bit significand.

if want handle platforms without such support:

i'm going assume long long 64-bit , double usual ieee 64-bit double.

if d >= 0x1.0p63, long long less it. if d < -0x1.0p63, long long greater it. if d != d, comparing should homecoming false because d nan. if fabs(d) >= 0x1.0p53, d represents integer, can convert d long long , comparing long longs. otherwise, can convert ll double , comparing doubles; if low bits lost, irrelevant comparison.

code (uncompiled , untested):

#define compar(a, b) ((a) < (b) ? -1 : (a) == (b) ? 0 : 1) int compar(long long a, double b) { if (b != b) homecoming false; if (b >= 0x1.0p63) homecoming -1; if (b < -0x1.0p63) homecoming 1; if (fabs(b) >= 0x1.0p53) homecoming compar(a, (long long)b); else homecoming compar((double)a, b); } #undef compar

c++ double long-long

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