I am trying to understand Chapter 3 Rank of Verbs in Henry's lab An
Introductory Course in J. Here one of his examples:
] array =: 2 3 4 $ 'abcdefghijklmnopqrstuvwx'
abcd
efgh
ijkl
mnop
qrst
uvwx
{."1 array NB. Select first item of each 1-cell
aei
mqu
Why isn't the result displayed as
a
e
i
m
q
u
?
The answer is that J always displays vectors horizontally, other arrays
vertically. An impractical but consistent display is provided by
showlist =: [: ": ,."1
which displays all arrays vertically:
showlist array
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
The array is a list of two tables, each a list of three vectors (here
displayed vertically), each a list of four letters.
showlist {."1 array
a
e
i
m
q
u
The result is a list of two vectors (here displayed vertically), each a
list of three letters. In the standard display, the vectors are
horizontal:
{."1 array
aei
mqu
By consistently showing lists vertically, verb showlist helps me
understand examples in Henry's Chapter 3.
Kip Murray
[EMAIL PROTECTED]
http://www.math.uh.edu/~km
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