Smalltalk experiment 1

Object subclass: Account [
    | balance |
    <comment:
        'I represent a place to deposit and withdraw money'>
    Account class >> new [
        <category: 'instance creation'>
        | r |
        r := super new.
        r init.
        ^r
    ]
    init [
        <category: 'initialization'>
        balance := 0.
    'initialized Account' printNl
    ]

    say [
        "say hello"
        ('I am account of balance "', balance printString, '".') printNl
    ]

    compute: val [
    | tar |
    tar := 3.
    balance := balance + val.
    ]

    mutate: array [
    (array at: 2) printNl.
    "array at: 2 put: -9." "NOTE: argument mutation is not allowed"
    ]
]

cl := [:x | |y| y := x + 1. "This is y = "
 ('This is y = ', y printString) printNl].
('y is ', y printString) printNl.

x0 := 1.
acc := Account new.
acc say.
acc compute: x0.
acc say.
acc class printNl.
array := #(1 2 3).
acc mutate: array.
array printNl.
cl value: 1.
('y is ', y printString) printNl.