[Jprogramming] sorry... hash tables again

[Jack Andrews]

i'm a beginner in J, but after doing a few labs, i have the old question:
 "where are hash maps"
from what i've gleaned, sparse arrays, something to do with e. and
m&i. are some answers
can i use the answer to speed up the example in the "mapped file database" lab?
can i build a competitor to kdb in j?
got to have big goals when you know nothing.