using Symata

FloatFormat(Short);

C = [a,[[a1,[a12,b12,c12]],[b2,[a22,b22,c22]],[c3,[a32,b32,c32,d32]]]];

trav(tree_List) := Flatten(trav([], tree), 1)
trav(accum_List, [x_, y_List]) := Map(yy -> trav([accum, x], yy), y)
trav(x_,y_) := Flatten([x,y])

trav(C)

Module({prev, prevprev, this},
begin 
    reset() := (prev = big"1"; prevprev = 1); 
    reset(); 
    nextFib() := (this = prev + prevprev; prevprev = prev; prev = this)
end
);

reset()

a = Table(nextFib(),[1000]);

a[-1]

ClearAll(a,b)

allsyms(expr_) := Cases(expr , s_Symbol => HoldComplete(s),[0,Infinity])

allsyms(a+b*(1-x))

[(-8)^(1/3), (-8.0)^(1/3)]

[CubeRoot(-8), Surd(-32,5)]

Surd(-8,4)

Surd(I,3)

VersionInfo()

Now()