include/o3tl/float_int_conversion.hxx

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   2 /*
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   9
  10 #ifndef INCLUDED_O3TL_FLOAT_INT_CONVERSION_HXX
  11 #define INCLUDED_O3TL_FLOAT_INT_CONVERSION_HXX
  12
  13 #include <sal/config.h>
  14
  15 #include <cmath>
  16 #include <type_traits>
  17
  18 namespace o3tl
  19 {
  20 // Return true iff `value` of floating-point type `F` converts to a value of integral type `I` no
  21 // smaller than `min`:
  22 template <typename F, typename I>
  23 std::enable_if_t<std::is_floating_point_v<F> && std::is_integral_v<I>, bool>
  24 convertsToAtLeast(F value, I min)
  25 {
  26     // If `F(min)`, `F(min) - F(1)` are too large in magnitude for `F`'s precision, then they either
  27     // fall into the same bucket, in which case we should return false if `value` represents that
  28     // bucket, or they are on the boundary of two adjacent buckets, in which case we should return
  29     // true if `value`represents the higher bucket containing `F(min)`:
  30     return value > F(min) - F(1);
  31 }
  32
  33 // Return true iff `value` of floating-point type `F` converts to a value of integral type `I` no
  34 // larger than `max`:
  35 template <typename F, typename I>
  36 std::enable_if_t<std::is_floating_point_v<F> && std::is_integral_v<I>, bool>
  37 convertsToAtMost(F value, I max)
  38 {
  39     // If `F(max)`, `F(max) + F(1)` are too large in magnitude for `F`'s precision, then they either
  40     // fall into the same bucket, in which case we should return false if `value` represents that
  41     // bucket, or they are on the boundary of two adjacent buckets, in which case we should return
  42     // true if `value`represents the lower bucket containing `F(max)`:
  43     return value < F(max) + F(1);
  44 }
  45
  46 // Return `value` of floating-point type `F` rounded to the nearest integer away from zero (which
  47 // can be useful in calls to convertsToAtLeast/Most(roundAway(x), n), to reject x that are
  48 // smaller/larger than n because they have a fractional part):
  49 template <typename F> std::enable_if_t<std::is_floating_point_v<F>, F> roundAway(F value)
  50 {
  51     return value >= 0 ? std::ceil(value) : std::floor(value);
  52 }
  53 }
  54
  55 #endif
  56
  57 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */