Using APL in shell

example.sh

# I needed to find the length of the longest filename
$ ls -1 *ttl
DatesAndTimes.ttl
download.ttl
exercise_log.ttl
gistHR0.2.0.ttl
nobel-prize-metaphacts-shacl-ontology.ttl
sample.ttl
SemArts2.0.0.ttl
visits_no_bnodes.ttl
visits.ttl
ABC-architecture.ttl

# A classic way
$ ls -1 *ttl | wc --max-line-length
41
# Note that you kind of just have to know about this command (wc) and this particular option (--max-line-length).
# You can't just stumble into it by building it up from primitives.

# Using APL in the shell (https://github.com/justin2004/apl_in_the_shell)
$ ls -1 *ttl | apl '⌈/≢¨' -
41
# In APL: ⌈/≢¨  means for each (¨) thing, take the tally (≢), then do a maximum (⌈) reduce (/)
# The "-" argument is a standard way of saying "use stdin as input"
# Note how I didn't have to discover the whole string '⌈/≢¨' in the first instance -- instead 
# I was able to build it up from the primitives incrementally.