Smalltalk Syntax Ina Postcard

SmalltalkSyntax In A Postcard

Short summary of SmalltalkSyntax and demonstration extreme simplicity.

This is copied from someone else, from whom I lost references. (If you know who is the original author, please edit. Also, this seems to be public domain. If you find it's not, also please edit.)

---

    exampleWithNumber: x
    "A method that illustrates every part of Smalltalk method syntax
    except primitives. It has unary, binary, and keyboard messages,
    declares arguments and temporaries, accesses a global variable
    (but not an instance variable), uses literals (array, character,
    symbol, string, integer, float), uses the pseudo variables
    true, false, nil, self, and super, and has sequence, assignment,
    return and cascade. It has both zero argument and one argument blocks."
    | y |
    true & false not & (nil isNil) ifFalse: [self halt].
    y := self size + super size.
    #($a #a "a" 1 1.0)
        do: [ :each |
            Transcript show: (each class name);
                       show: ' '].
    ^x < y

---

This covers almost all syntax in SmalltalkLanguage.

Although it states it accesses a "global variable (but not an instance variable)", it also accesses a method temporary, which shares the syntax with instance variables. Just remove the "| y |" bit and the later mention to y is an instance variable.

Some things not covered (besides primitives) are:

• Squeak brace arrays. Though they're not standard, they're becoming more and more common across dialects.

    myBraceArray := {y. y + x. 'a string', ' concatenation'}.
    "myBraceArray has 3 elements:
      1-the object referenced by y at the time of creation.
      2-the result of sending '+ x' to y at the time of creation.
      3-the result of sending "", ' concatenation' "" to "" 'a string'
        ('a string concatenation', if you didn't mess with String class)."

• The also not standard but really common block temporaries:

    [ :w :x | "<- this are block parameters"
       | y z | "<- and this block temporaries"
       "..."
     ]

• The not standard, not common, and sometimes ConsideredHarmful use of '_' instead of ':=':

     x := y. "a binding"
     y _ x. "also a binding"

Note: Dialects that understand '_' will usually print it as a left pointing arrow (mimicking original Smalltalk code).

Also, AllStatementsAboutSmalltalkAreFalse. ;) Oh, yeah, and SyntaxFollowsSemantics.

fs.

---

CategorySmalltalk