We assume the sequence of expressions is in a valid order (all items available before use). This function partitions the expressions into ordered longest "no new value used blocks" by greedily scanning forward remaining expressions in order taking any that: have all their values available from earlier groups, do not use a value formed in the current group, and do not overwrite a value formed in the current group. For an example please see https://winvector.github.io/FluidData/partition_mutate.html.
mutate expressions with := used for assignment.
ordered list of mutate_se assignment blocks
partition_mutate_qt does not perform
plan <- partition_mutate_qt(a1 := 1, b1 := a1, a2 := 2, b2 := a1 + a2) print(plan)#> $group00001 #> a1 a2 #> "1" "2" #> #> $group00002 #> b1 b2 #> "a1" "a1 + a2" #>#> x a1 a2 b1 b2 #> 1 1 1 2 1 3