There's a guide here! https://vmchale.github.io/jacinda/
When I think about how I use awk, I think it’s mostly something like:
awk '!a[$2]++' # first occurrence of each value in the second field
awk '{a[$2]+=$3} END {for(x in a) print x, a[x]}'
awk '{ print $1, $3, 1, $2; print $1+20, $3, -1, -$2}' | sort -n | awk '{ a[$2]+=$3; b[$2]+=$4; print $1, $2, b[$2]/a[$2] }'
The awk features that feel ‘non-functional’ to me are less the mutation and more operations like next, or the lack of compositionality: one can’t write an awk program that is, in some sense made of several awk programs (i.e sets of pattern–expr rules) joined together. That compositionality is the main advantage, in my opinion, of the ‘functional’ jq, which feels somewhat awk-adjacent. Is there some way to get composition of ja programs without falling back to byte streams in between?
(->2)"(->1)~.*{|`2.`0}
"(\g. g.((+)|0 {g=`2}{`3})) ~. $2
I’m not sure I really understand the language (and I definitely don’t understand the implementation!) but it seems pretty interesting. Perhaps a better motto than “functional awk” is “streaming APL with type checking (and type classes)”?
The colon being used in multiple contexts is tricky. As I was scanning the examples I found postfix `:` doing type conversion like in `(%)\. {%/Apple/}{`3:}` and then I was wondering what it does when it has nothing on its left-hand side, like in `[(+)|0 [:1"x]`. Then I noticed that the [ were unbalanced in the latter example, and eventually figured out that `[:` is its own operator separate from `:` and the middle `[` had nothing to do with function syntax.