>
> Cool. Intriguing.
>
> I'm sure I can use it to:
> - patch problematic code on the fly without registering an override
> - change the semantics of some smalltalk statement (so that a := becomes self
> a: or anything else)
>
Yes, it is for “evil” experiments that can not be done else (short of changing
the compiler itself).
e.g. last week for an experiment, I wanted a form of “super” where it is not
“self, but start lookup in superclass”, but instead
“this object, do a send to it but start lookup in the superclass”. There are
no messages called #super in the image, so you can
so that by transforming all
myObject super doSomething
into
myObject perform: #doSomething withArguments: #() inSuperclass: myObject class
superclass.
The needed Opal plugin has this #transform method:
transform
| superSends new |
superSends := ast sendNodes select: [ :each | each selector = #super ].
superSends do: [ :spnode |
new := RBMessageNode
receiver: spnode receiver copy
selector: #perform:withArguments:inSuperclass:
arguments: {RBLiteralNode value: spnode parent selector
copy .
RBArrayNode statements: spnode parent arguments
.
RBMessageNode receiver: (RBMessageNode
receiver: spnode receiver copy selector: #class) selector: #superclass}.
spnode parent replaceWith: new
].
^ast
> Would it be possible to couple it with Clement work to have some ability to
> pre-compile some code in specific classes (strength reduction, once literals)
> where we know that this is valuable?
>
Good question….
> It would also be nice to have a way not to write bytecode by hand, like, say,
> in the slots example of a few days back.
>
Yes, the byte code writing for Slots is just a solution that works *today*.
With a runtime optimizer you could instead always generate the reflective slow
version
and let Sista optimise it.
> Oh, ok, for the literal stuff, I think I know how to do it:
>
> In a method:
> - replace target expression with symbol literal.
> - evaluate target expression in isolation, store value.
> - compile method with symbol literal.
> - in compiled method, replace symbol literal with value stored above.
>
> Would that work?
>
Hmm… messages to known objects without side effect could be evaluated by the
compiler.
What makes it hard ist mostly debugging: mapping the generated code back to the
original
source….
Marcus
