We also make use of factorials as we divide exponentiated values by a factorial of exponents thereof. The factorial of a given number n is the product of all positive integers less than or equal to the given number n:

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;
; Simple calculation of factorial
; Parameter is in ECX (number to calculate the factorial of)
; Return value is in XMM0 register
;-----------------------------------------------------
fact:
   push ebp
   mov ebp, esp
   sub esp, 16 * 3

   push ecx
   movups [ebp - 16], xmm1
   movups [ebp - 16 * 2], xmm2
   mov dword[ebp - 16 * 3], 1.0
   movd xmm2, [ebp - 16 * 3]
   movlhps xmm2, xmm2
   movsldup xmm2, xmm2
   movaps xmm0, xmm2
   movaps xmm1, xmm2

.l1:
   mulps xmm0, xmm1
   addps xmm1, xmm2
   loop .l1

   movups xmm2, [ebp - 16 * 2]
   movups xmm1, [ebp - 16]
   pop ecx
   mov esp, ebp
   pop ebp
   ret