Smalltalk syntax note

Hello!

In the comments to the topic, people were interested in the Smalltalk brand features. This note would like to slightly disclose the comment of the user mou and put the main emphasis on the simplicity of the language.

In order to program using the Smalltalk language, it’s enough to know 2 concepts:

• absolutely everything is an instance of any class
• an instance of the class can send a message

In addition, you can send a message to the class itself, since the class, in turn, is also an instance ( Chicken or egg? ).
It should be noted that the language supports:

• assignment operation ( := )
• return operation ( ^ )
• variable declaration block ( | <_1> <_2> | )
• template for creating an array of values ​​( #( _1 _2 ) )
• code block ( [ : <> | < > ] )

With the help of the message sending mechanism, all operations familiar to programming languages ​​are implemented: loops, conditional jumps, etc.
Messages sent to an object (class instance) can be of three types:

• Unary
  object message
  Example: #('' '' '') size
  - an instance of the Array class is sent a size message, whose processing method will return the size of the message recipient. In this case, the recipient of the message is #('' '' '') , and the message processing method size returns the value 3.
• Binary
  object message object argument
  Example: 10 - 5
  - a message - sent to the instance of the SmallInteger class - 10 - (minus), with one argument - the SmallInteger class instance - 5 . Message processing method - (minus) returns the difference between the recipient (10) and the argument (5). It should be noted that the recipient of the message may be the result of performing any operation. So in expression 6 - 2 * 3 recipient of the message * will be the result of operation 6 - 2 and in response to the message * returns 12, not 0, as one would assume. In order to change the order of calculations, brackets should be used, which will make it possible to treat the expression inside the brackets as an argument to the message in front of it. Messages of this type must necessarily consist of one or two special characters (+, =,! =, //, \\, etc.).
• Key
  object cl_word_commun_1: object argument [ cl_word_company_n: object argument]
  Example: Transcript show: 'Hello!'
  Example: CwTextPrompter prompt: ' ?' answer: '' title: '...' CwTextPrompter prompt: ' ?' answer: '' title: '...'
  - the message is a set of keywords in a strictly defined order. The keywords are separated by a colon, and after each keyword an argument object must follow. So in the first example, the message consists of just one show keyword, followed by a string - an argument object. The second example message consists of three keywords: prompt: answer: title: set of keywords in a certain order is a message. It is recommended to place the words in the message so that when the message is written along with the argument objects, the expression reads like a sentence in natural language.

As an example, I will give the method of processing a binary message * which multiplies the receiver matrix by the argument matrix:
')

* rcMatrix
" "

" "
| r |
" r new:with: RCMatrix"
r := RCMatrix new: (self rowsCount) with: (rcMatrix columnsCount).

" "
1 to: (self rowsCount) do:
[:i |
1 to: (rcMatrix columnsCount) do:
[:j |
r at: i at: j put: 0.
].
].

""
1 to: (self rowsCount) do:
[:i |
1 to: (rcMatrix columnsCount) do:
[:j |
1 to: (rcMatrix rowsCount) do:
[:k |
r at: i at: j put:
((r at: i at: j) +
((self at: i at: k) * (rcMatrix at: k at: j))).
].
].
].

" "
^r.

* This source code was highlighted with Source Code Highlighter .

Thank you for your attention to the note.