Position BinarySearch( List L, ElementType X )
{
int left,right,mid;
left=1;
right=L->Last;
while(left<=right)
{
mid=(left+right)/2;
if(X<L->Data[mid])
right=mid-1;
else if(X>L->Data[mid])
left=mid+1;
else
return mid;
}
return NotFound;
}