Smalltalk/X Cheat Sheet

A short, one page summary of what beginners need to know about syntax and ST/X command line arguments on one page. Non standard ST/X extensions are marked with (*).
A list of most useful messages is found in the "List of Useful Selectors"

Syntax

Comments

Regular comment	`" this is a comment "`
EOL-Comment (*)	`"/ this is an End-of-Line comment`
Token-Comment (*)	`"<<END a multiline token-comment up to a line starting with 'END' more commented stuff here ... comment ends here END`

Literal Constants

Integers	`12345 -12345`
Large integers	`1234567890123456789012345...` (arbitrary size)
Integers with radix	`16rAFFE 0xFEED 16r-AFFE -0xBEAF -16rAFFE 2r010101 0b11011 2r-010101 -0b1100 8r0777`* the 0x, 0b variants are non-standard
Floats (IEEE double; roughly 17 decimals)	`12.456 1.234e17 -6.9 -6e-10 Float pi Float e`
Short floats (IEEE single; roughly 8 decimals)	`1.234f17 -6f-10`
Long floats (IEEE quad; roughly 20 decimals) (*)	`1.234q17 -6q-10`
Fractions	`(1/3) (17/2)`
Characters	`$a Character space Character nl` Also: "`null`", "`tab`", "`return`", "`bell`"...
Strings	`'hello'` with C-escape sequences (): `c'hello\nworld'` with embedded expressions (): `e'it is {Time now}\nHave fun'` internationalization (): `i'Sunday'` or `i'Sunday {Date today}'` regex (): `r'a'` or `r'[a-z][0-9a-z]'`
Symbols	`#'hello'` `#foo` (without quotes, if only alphaNumeric characters)
Arrays	`#( el1 el2 ... elN )` each element a literal constant
Byte arrays	`#[ b1 b2 ... bN ]` each byte-element an integer constant in 0..255
Special number arrays (*)	`#XX( v1 v2 ... vN )` XX: is one of 'u8', 's8', 'u16', 's16', 'u32', 's32', 'u64', 's64', 'f32', 'f64' and each element being an integer or float constant
Immediate Inline Objects (*)	`#{ foo: fooValue . bar: barValue }` fooValue and barValue: constant

Blocks (aka Lambdas / Closures)

Without argument	`[ expr1 . expr2 ... exprN ]` when evaluated (by sending it the "value" message), the value is the value from the last expression, exprN
One argument	`[:arg \| expr1 . expr2 ... exprN ]` evaluate by sending it the "value:" message
Multiple arguments	`[:a1 :a2 ... :aN \| expr1 . expr2 ... exprN ]` evaluate by sending it a "value:...value:" message

Expressions

the receiver expression is evaluated, then multiple messages (separated by ";") are sent to this receiver.
The value of the cascade is the value returned by the last message.

Unary Expression (without argument)	`receiver messageName` receiver is itself either a constant, a lambda-block, a unary expression or a parenthesized expression
Keyword Expression: (1 arg)	`receiver messageNamePart:argExpression` whitespace between the colon and the argExpression is optional.
Keyword Expression: (any number of args)	`receiver messageNamePart1:argExpression1 messageNamePart2:argExpression2 ... messageNamePartN:argExpressionN`
Binary Expression	`receiver binOP arg` with binOP being any combination of special characters: * , + , - , % , & , / , \ , \| , = , < , > , ? and , I.e. "`foo ==> 123`" is the binary message "`==>`" sent to `foo` with `123` as argument. And "`foo ? 123`" is the binary message "`?`" (or-if-nil) sent to `foo` with `123` as argument. And "`foo , bar`" is the binary message "`,`" (concatenation) sent to `foo` with `bar` as argument.
Cascade Expression (sending multiple messages to the same receiver)	`receiver message1 ; message2 ; ... messageN`
Parentheses for grouping	`( any expression )`
Assignment	`variable := expression` can be used as expression.
Computed Array (Brace Construct)	`{ expr1 . expr2 . ... . exprN }` instantiates a new Array object with elements from the expressions.
Computed Inline Objects (*)	`{ foo: fooExpr . bar: barExpr }` fooExpr and barExpr are expressions. Notice the period to separate fields.

Remaining Syntax

Local variables (in block or method)	`\| var1 var2 ... varN \|` variable declarations must be at the beginning, before any expression.
Separating multiple expressions (sequence)	`expr1 . expr2 . ... exprN` expressions (statements) are separated by fullstop (period) characters. The last expression may or may not be followed by a fullstop; if there is one, this is treated like a followup empty statement.
Return from method	`^ expression` returns from the enclosing method (also if inside a block-closure)

Wellknown (Common) Messages

Conditional Execution	`boolExpr1 ifTrue:[ ... ] ifFalse:[ ... ]` variations without true part (ifFalse:), without false part (ifTrue:) and with the order reversed (ifFalse:ifTrue:) are available.
While-Loop	`[ boolExpr1 ] whileTrue:[ ... ]` notice the receiver being a block. A whileFalse variant is also available. Loops with test at end are written as "[...] doWhile:[...]" or "[...] doUntil:[...]"
For-Loop	`start to:stop do:[:iterVar \| ... ]` evaluates the lambda for each value in start..stop.
Enumerating Collections	`collection do:[:elementVar \| ... ]` evaluates the lambda for each element in the collection.
Evaluating a Lambda Block without arguments: with arguments:	`aBlock value` `aBlock value:expr1 ... value:exprN` the number of arguments must match the number expected by the lambda (although varArg lambdas are also available)
Starting a background thread	`aBlock fork` evaluates the lambda in a separate thread. Alternatives are "forkNamed:" to give the thread a user friendly name.

Wellknown Globals

Logging and Messaging Logger - redefinable logger (defaults to standard error)
Transcript - console window
Stdout - standard output
Stderr - standard error
Stdin - standard input

Most Wellknown Classes

Numbers	`Number` (abstract superclass) `Integer` (integral numbers), `Float` (inexact) `Fraction`(exact) `Complex` a few more...
Collections	`Array` (fixed size array) `OrderedCollection`, `List` (variable size) `SortedCollection` `Set`, `Bag` (unordered) `Dictionary` (mapped collections) `BinaryTree`, `AVLTree` `SharedQueue` (shared, synchronized) many more...
Process Handling	`Process` (lightweight thread) `OSProcess` (heavyweight OS process) `Semaphore`, `RecursionLock` (synchronization) `Monitor`, `BoltLock` `Delay`
Files & Streams	`Filename` (file naming, directory access, mime type) `Stream` (basic stream framework) `ReadStream`, `WriteStream`, `EncodedStream` `ExternalStream`, `FileStream`, `Socket` (OS streams)
Low Level Access	`OperatingSystem` (OS API calls) `Smalltalk` (startup, shutdown and globals) `ObjectMemory` (VM access)

Command Line

A more complete description is found in the Command Line section of the getting started document.

-I	ignore snapshot image
--quick	quick startup; no banner shown
--repl	start an interactive read-eval-print-loop
--print expr	eval expr, print its value then exit
--eval expr	eval expr (without printing) then exit
--execute filename	execute the script in fileName then exit
--loadPackage package-ID	preload a compiled smalltalk class library (package)
--help	show all other command line options

<cg at exept.de>

Doc $Revision: 1.17 $ $Date: 2021/06/14 16:20:31 $