macro
   hypergeometric x A B n PxABn

#This macro calculates the hypergeometric distribution
#h(x;A,B,n). The funny order of the different terms is
#necessary to avoid overflow errors in the factorials.

#Example call:
#   mtb> %hypergeometric 2 6 24 5 k1

mconstant x A B n PxABn AplusB i nminusx

let AplusB=A+B
if (x<0) or (x>n) or (x>A) or (n<0) or (n>AplusB)	#invalid cases
   let PxABn=0
elseif (x=0)					#special case x=0
   let PxABn=1
   do i=1:n
      let PxABn=(B+1-i)/(A+B+1-i)*PxABn
   enddo
else						#x>0
   let PxABn=1
   do i=1:x
      let PxABn=(A+1-i)/(x+1-i)/(A+B+1-i)*(n+1-i)*PxABn
   enddo

   let nminusx=n-x
   do i=1:nminusx
      let PxABn=(B+1-i)/(A+B-x+1-i)*PxABn
   enddo
endif

print PxABn

endmacro