Am Samstag, 7. Oktober 2006 21:41 schrieb Martin Drautzburg:

> As a sidenote: I have difficulties to understand how Smalltalk works,
> especially the way method calls eventually resolve to primitive calls.

Take this method in Object for example:

Object>>basicAt: index put: value 

	"Primitive. Assumes receiver is indexable. Store the second argument 
	value in the indexable element of the receiver indicated by index. Fail 
	if the index is not an Integer or is out of bounds. Or fail if the value is 
	not of the right type for this kind of collection. Answer the value that 
	was stored. Essential. Do not override in a subclass. See Object 
	documentation whatIsAPrimitive."

	<primitive: 61>
	index isInteger
		ifTrue: [(index >= 1 and: [index <= self size])
					ifTrue: [self errorImproperStore]
					ifFalse: [self errorSubscriptBounds: index]].
	index isNumber
		ifTrue: [^self basicAt: index asInteger put: value]
		ifFalse: [self errorNonIntegerIndex]

The thing in the brackets

<primitive: 61>

is a primitive call. The number 61 tells the VM which primitive to execute. 
(There are also named primitives which were added later on.)

If the primitive succeeds then the method returns. If the primitive fails then 
the rest of the method is executed, in this case an attempt to recover or 
give a meaningful failure message.

> I'd 
> be most grateful for an explanation the other way round, i.e. starting with
> the primitives and the way the entire system builds up from them.

Read

http://users.ipa.net/~dwighth/smalltalk/bluebook/bluebook_imp_toc.html

for a description of the ST80 virtual machine (the ancestor of the Squeak VM).

Regards, Lothar