Python: why do functions in math module accept Decimal objects as arguments? -

bizzarely, every function python's math module seems work fine decimal objects. example: frexp, exp, cos.

when type print(math.frexp(decimal.decimal('2341.12412'))), python prints correct answer, (0.57156... , 12), , doesn't throw exceptions.

i assume math module written in low-level c, relying heavily possible on hardware math operations efficiency. so... why work decimal objects?

did put type check math functions, , switch different implementation if argument decimal? didn't see mentioned in docs. decimal automatically being converted float, doesn't make sense, either.

yeah, i'm confused.

well looking @ math module.c got this:

static pyobject * math_frexp(pyobject *self, pyobject *arg) {     int i;     double x = pyfloat_asdouble(arg);     if (x == -1.0 && pyerr_occurred())         return null;     /* deal special cases directly, sidestep platform        differences */     if (py_is_nan(x) || py_is_infinity(x) || !x) {         = 0;     }     else {         pyfpe_start_protect("in math_frexp", return 0);         x = frexp(x, &i);         pyfpe_end_protect(x);     }     return py_buildvalue("(di)", x, i); } 

looking @ code, in fact use float (pyfloat_asdouble)

again same thing exp,

static pyobject * math_factorial(pyobject *self, pyobject *arg) {     long x;     pyobject *result, *odd_part, *two_valuation;      if (pyfloat_check(arg)) {         pyobject *lx;         double dx = pyfloat_as_double((pyfloatobject *)arg);         if (!(py_is_finite(dx) && dx == floor(dx))) {             pyerr_setstring(pyexc_valueerror,                             "factorial() accepts integral values");             return null;         }         lx = pylong_fromdouble(dx);         if (lx == null)             return null;         x = pylong_aslong(lx);         py_decref(lx); .........................................................