[Swift-devel] dataset marking

[Ben Clifford]

The present SwiftScript->karajan compiler contains a bunch of code to do 
'dataset marking'.

Its a bit tangled, as the other code has evolved around it, and my 
understanding of it is correspondingly tangled. So please speak out if 
there is a problem with the following.

The purpose of the dataset marking is to identify which dataset 
declarations in a SwiftScript program are inputs (to the whole workflow) 
and mark them as such in the compiled code. A dataset is an input if it is 
never assigned to; if it is assigned to then it is not an input.

I worked on some code that changes the way that arrays are closed, by 
identifying which statements write to a dataset, at compile time.

This information is also what is needed, I think, to do the above 
mentioned dataset marking - the same code which finds out that some 
statements are writing to a dataset will also find out that some datasets 
have no statements at all writing to them.

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