Append(expr, item)
returns
exprwithitemappended to its leaves.
>> Append({1, 2, 3}, 4)
{1,2,3,4}
Append works on expressions with heads other than List:
>> Append(f(a, b), c)
f(a,b,c)
Unlike Join, Append does not flatten lists in item:
>> Append({a, b}, {c, d})
{a,b,{c,d}}
Nonatomic expression expected.
>> Append(a, b)
Append(a,b)