libcxx/test/std/numerics/numarray/valarray.nonmembers/valarray.transcend/valarray_helper.h

   1 #ifndef LIBCPP_TEST_VALARRAY_HELPER_H
   2 #define LIBCPP_TEST_VALARRAY_HELPER_H
   3
   4 #include <cmath>
   5
   6 // Returns whether `x` and `y` are equal, up to the given number of
   7 // significant digits after the decimal.
   8 //
   9 // Specifically, we look whether `abs(x - y) < epsilon`, where epsilon
  10 // is `(1 / 10)^p`, assuming p is the number of digits we care about.
  11 // This means we're basically looking whether `abs(x - y)` is less
  12 // than `0.00..001` for some number of digits.
  13 inline bool is_about(double x, double y, int significant_digits) {
  14     double epsilon = std::pow(1.0 / 10.0, significant_digits);
  15     return std::abs(x - y) < epsilon;
  16 }
  17
  18 #endif /* LIBCPP_TEST_VALARRAY_HELPER */