[Swift-devel] Swift Question/Request

[Mihael Hategan]

How exactly does seq make Swift know how many outputs processStageOne()
has?

On Tue, 2007-04-03 at 10:25 -0500, Tiberiu Stef-Praun wrote:
> Sometimes i find myself in the position of wanting to do one step of
> the swift script only after the previous phase has finished. The case
> is the following (not really swift script):
> 
> seq{
> file stageOneOutputs[] = processStageOne();
> file combine = combine(stageOneOutputs);
> }
> 
> In my case the problem seems to be the fact that swift cannot dream up
> how many stageOneOutput files will exist (unless we extend the
> language -probably the input mapper which I use in this case- to
> support this feature), so it could decide to start the combine stage
> prematurely.

I seriously doubt that. It may not start it at all, but prematurely, no.

> Supposedly one solution is to create a dummy output file at the end of
> stage one, and pass it tot stage two.
> 
> Any suggestions ?

This kind of problem can only be addressed in two ways:
1. You know how many files you have when you write your program (and use
a fixed array mapper).
2. Swift can figure out how many files are out there. This is something
that, by virtue of the number of times we've seen this cropping and the
fact that there is no hack that can solve it, should be on our list of
things (if not already there).

> 
> I'm thinking that having an example in the user guide would help others as well.
> Maybe we should have a "Patterns in Swift" document.
> 
> Thanks
> Tibi
>