2.25.16 Number of zeros in [a,b[ : sturmab
sturmab takes four arguments: a polynomial expression P, a
variable name and two real or complex numbers a and b

if a and b are reals,
sturmab returns the number of sign changes of P on ]a; b].
In other words, it returns the number of zeros in [a,b[ of the
polynomial P/G where G=gcd(P,diff(P)).
 if a or b are complex,
sturmab returns the number of complex roots of P in the rectangle
having a and b as opposite vertices.
Input :
sturmab(x^
2*(x^
3+2),x,2,0)
Output :
1
Input :
sturmab(x^
31,x,2i,5+3i
Output :
3
Input :
sturmab(x^
31,x,i,5+3i
Output :
1
Warning !!!!
P is defined by its symbolic expression.
Input :
sturmab([1,0,0,2,0,0],x,2,0),
Output :
Bad argument type.