Proposal: generator#clone() and generator#goto()

Salvador de la Puente González salva at
Wed Aug 20 05:00:32 PDT 2014


Just a little presentation before the proposal. I'm Salvador de la Puente
González (you can call me Salva, please). I'm working for Telefonica I+D in
Mozilla Firefox OS and I'm a front-end developer, you can know more about
me in and my github user is

Now, these day I was thinking about a generator feature. I have a use case
for a transpiler I'm developing: in the source language you have procedures
much more like Linux processes. The language have a block sentence *clone*
for cloning a procedure. After cloning, father procedure simply ignores the
block while coned procedure execute sentences inside. Like an automatized
|pid = fork() if (pid != 0) { .... }|.

Now I'm addressing this problem from a AST perspective, transpiling
procedures to a special generators able to fall through their sentences
until reaching a specific yield.

But I think it could be easier if I could do something like
*|generator#clone()|* returning a new generator object. This new generator
is paused of the same yield as the original one and have a new variable
environment with a shallow copy of the original's variable environment. The
variable environment's parent chain would be the same as the original one.

Notice this is not related with data preservation as most of the objects
being used by original generator will be shared with the new one (although
this could be addressed as well) but with execution state.

In the same way, to provide a complete control over execution state inside
generators I would like to propose *|generator#goto(yieldLabel)|* that
could allow the developer to transfer the execution cursor to a labeled
yield sentence. The result of the yield sentence could be the extended with
the label for that yield.

I know it does not suffice to be a cool feature but I think it could
trigger very interesting uses cases and applications in backtracking or
temper algorithms.

What do you think?
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