C isn't very readable either which is why commenting is encouraged. But the Obfuscated C Contest is a competition whereas APL is literally the punchline for illegibility.
result←findMax data
max←0
:For i :In data
:If i>max
max←i
:EndIf
:EndFor
result←max
then findMax 5 1 2 3 5 6 3 1
6
Writing it more neatly as findMax←⌈/ isn't mandatory anymore than `reduce(max, numbers)` is mandatory in Python.But I remember what confused me the most was trying not to use loops to sum arrays and using vector ops like +/A