Comment by listeria

weirdly enough, the provided implementation of rand_float() actually generates numbers in the interval [0, 1).

I haven't read the implementation of _generate_canonical_generic(), but the following special case in generate_canonical() applies here:

  if constexpr (prng_is_bit_uniform && sizeof(T) == 4 && sizeof(generated_type) == 8) {
    return (static_cast<std::uint32_t>(gen()) >> exponent_bits_32) * mantissa_hex_32;
  }

which boils down to:

  return (static_cast<std::uint32_t>(gen()) >> 8) * 0x1.p-24;

that is, a number in the interval [0, 2^24) divided by 2^24.