collections "arithmetics" commands

[nitzantomer]

Examples:
list:

[1, 2, 3] + [4, 5]
// is
[1, 2, 3, 4, 5]

[1, 2, 3] - [2, 4]
// is
[1, 3]

map:

{ str: string } + { num: 4 }
// is
{ str: string, num: 4 }
// but
{ str: string, num: 5 } + { num: 4 }
// is
{ str: string, num: 5 }
// so:
{ str: string, num: 5 } ++ { num: 4 }
// is
{ str: string, num: 4 }

{ str: string, num: 5 } - [num]
// is
{ str: string }