ctanhf
float complex ctanhf(float complex);
z = ctanhf(CMPLXF(cimagf(z), crealf(z)));
debug("%a %a\n", creal(ctanhf(z)), cimag(ctanhf(z)));
test_odd_tol(ctanhf, z, CMPLXL(tanhf(nums[i]), 0),
test_odd_tol(ctanhf, z, CMPLXL(0, tanf(nums[i])), FLT_ULP());