IBM 5110 User Manual page 28

Indices (whatever is inside the brackets) can be expressions, provided
that when those expressions are finally evaluated, the results are
values that represent valid indices for the array:
B
ABCDEFGHIJKLMNOPQRSTUVWXYZ
XE"1 2 3 4· 5
B[X)(2:J
BDFH.J
x
1231+~:5
B [1'" X)( :3::1
DGJMP
The array from which elements are selected does not have to be a
variable. For example,a vector can be indexed as follows:
2 3 5 7 9 11 13 15 17 19[7 2 ~ 2::1
13 3 7 3
'ABCDEFGHIJKLMNOPQRSTUVWXYZ '[12
15 15 11 27
16 1]
LOOK PA
DDN
MAI~Y
'ABCDEFGHIJKLMNOPQRSTUVWXYZ '[2
~p~
15
14 27 13 1 18
25]
Indexing a matrix or N-rank array requires an index number for each
coordinate. The index numbers for each coordinate are separated by
semicolons. Suppose M is a 3 by 4 matrix of consecutive integers:
If you ask to see the values of M, they are displayed in the usual
matrix form:
M
1 2 3
' +
I:!"
,J
6 '7 8
9
10
11 1")
.
.:..
If you want to refer to the element in row 2, column 3, you enter:
7
If you want to refer to the third and fourth elements in that row, you
enter:
7 8
APL Language Elements 23