Sequence

Sequence[x1, x2, ...]

represents a sequence of arguments to a function.

Sequence is automatically spliced in, except when a function has attribute SequenceHold (like assignment functions).

>> f(x, Sequence(a, b), y)
f(x,a,b,y)

>> Attributes(Set)
{HoldFirst,Protected,SequenceHold}

>> a = Sequence(b, c);

>> a
Sequence(b,c)

Apply Sequence to a list to splice in arguments:

>> lst = {1, 2, 3};

>> f(Sequence @@ lst)
f(1,2,3)

Inside Hold or a function with a held argument, Sequence is spliced in at the first level of the argument:

>> Hold(a, Sequence(b, c), d)
Hold(a,b,c,d)

If Sequence appears at a deeper level, it is left unevaluated:

>> Hold({a, Sequence(b, c), d})
Hold({a,Sequence(b,c),d})