# log integral;
#li(n_,x_) := If(n>=1, -n*li(n-1,x)+ln(x)^n*x,
	If(n<-1, (-li(n+1,x)+ln(x)^(n+1)*x)/(n+1)));

li(n_,0) := 0;
li(n_,1):=zeta(n);
li(n_,inf) := inf;
li(n_,-inf) := 0;
li(1,x_):= -log(1-x);
li(0,x_) := x/(1-x);
li(-1,x_) := x/(1-x)^2;
#li(0,0) := 0;

li(e^x_):=ei(x);
li(0):=0;
li(1):= -inf;