This stage represents Normalization Stage1: Symbolic Reduction in Philip Wadler's Paper
"A Practical Theory of Language Integrated Query", given in Figure 11.
http://homepages.inf.ed.ac.uk/slindley/papers/practical-theory-of-linq.pdf
It represents foundational normalizations done to sequences that represents queries.
In Wadler's paper, he characterizes them as for x in P ... whereas in Quill they are
characterized as list comprehensions i.e. P.flatMap(x => ...).
This stage represents Normalization Stage1: Symbolic Reduction in Philip Wadler's Paper "A Practical Theory of Language Integrated Query", given in Figure 11. http://homepages.inf.ed.ac.uk/slindley/papers/practical-theory-of-linq.pdf
It represents foundational normalizations done to sequences that represents queries. In Wadler's paper, he characterizes them as
for x in P ...
whereas in Quill they are characterized as list comprehensions i.e.
P.flatMap(x => ...).