what is the proper way to use multidimensional maps

[alperyilmaz]

I'm having difficulty generating multidimensional maps with frawk.

let's try to get yearly sales report for some products. here's data

$ echo -n -e "year,product,sold\n2021,A,50\n2021,B,100\n2021,A,70\n2020,A,10" > sales.csv
$ cat sales.csv
year,product,sold
2021,A,50
2021,B,100
2021,A,70
2020,A,10

with awk we can do

$ awk -F"," 'NR>1 {sales[$1][$2] += $3}END{for (year in sales){ for (prod in sales[year]){print year, prod, sales[year][prod]}}}' sales.csv
2020 A 10
2021 A 120
2021 B 100

let's try with frawk (I omitted print part, just trying to build the map)

$ cat sales.csv | frawk -icsv -H '{sales[$1][$2] += $3}'
error compiling cranelift: [src/types.rs:525:40] kinds do not match. Map { key: None, val: Some(Int) } vs Scalar(None)

what is the trick to generate multidimensional maps in frawk? do we need some sort of initialization at the beginning?