[GiNaC-list] substitute for step ( wild ( ) ) function derivative

[jros]

	I found this solution, tah I exemplify

	symbol my_wild;
	ex my_wild_ex;
	my_wild_ex=subs(diff(step(my_wild),my_wild), my_wild==wild());
	
	ex U=.....*step(....);
	ex equation_1=diff(U,theta);
	equation_1.subs(my_wild_ex == 0);

	So D[0](step) disappear from equation_1

	Thanks,

	Javier