[Newbies] Questions about primitives - how to avoid one ?

[David T. Lewis]

On Sun, Feb 17, 2008 at 11:30:18PM +0100, cdrick wrote:
> For whatever reasons, I want sometimes to experiment some smalltalk
> code by avoiding a primitive call, like in Float>>=, which start by
> <primitive:47>. Only commenting doesn't work. So, is it possible ? and
> if the primitive fail, is the smalltalk code evaluated ?

If you comment out the primitive like this is should definitely work:

> aNumber 
	"Primitive. Compare the receiver with the argument and return true
	if the receiver is greater than the argument. Otherwise return false.
	Fail if the argument is not a Float. Essential. See Object documentation
	whatIsAPrimitive."

	"<primitive: 44>"
	^ aNumber adaptToFloat: self andSend: #>

And yes, if the primitive fails, the alternative Smalltalk (after the
"<primitive: 44>" is evaluated.

> Out of curiosity, where can we find the "primitive 47" code ? I
> imagine in the source of the VM...  but if someone can give me some
> insights :)

Load the VMMaker package to see the source code. Look at
Interpreter class>>initializePrimitiveTable to find the method that
implements primitive 47, which is #primitiveFloatEqual. Find implementers
of #primitiveFloatEqual, and you will have the Smalltalk source code.
This will be translated from Smalltalk to C when you generate the VM,
and the resulting C is what implements the primitive.

Dave