fostr/trans/desugar.str
Glen Whitney 7c69b82484
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feat WIP: checkpoint initial efforts on stream extraction
Adds ! operator and !! expression, with Python code gen and
  an item in tour.
  Still needs: other languages, check generated docs, and addition
  of standard input to test scheme.
2021-03-01 20:51:12 -08:00

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module desugar
imports libstrategolib signatures/-
rules
/* ISequence() and Prior() are just noise for more expressions in sequence,
put in to get the layout rules right. So we remove them and collapse
all occurrence of them into one big Sequence() call on a list.
This is slightly tricky because there might not be any Sequence() call
at the top level, but yet an ISequence(). So we do it in two passes,
first converting ISequence()s to Sequence()s, and then collapsing
Sequence()s.
*/
deISe: ISequence(Prior(l),x) -> Sequence(<conc>(l, [x]))
seqFlatten: Sequence(l) -> Sequence(<mapconcat(?Sequence(<id>) <+ ![<id>])>l)
defStream: DefGets(x) -> Gets(Stream(), x)
defStream: DefTo(x) -> To(x, Stream())
defStream: DefEmits() -> Emits(Stream())
strategies
desugar-fostr = bottomup(try(defStream <+ deISe <+ seqFlatten))