X is the name of a variable in the workspace, possibly modified by the indexing function (EXP X[I])←Y, see Assignment (Indexed). EXP is an expression that selects elements of X. Y is an array expression. The result of the expression Y is allocated to the elements of X selected by EXP. Note that X may refer to a single name only.
The following functions may appear in the selection expression. Where appropriate these functions may be used with axis [] and with the Each operator ¨.
Functions for Selective Assignment
| ↑ | Take |
| ↓ | Drop |
| , | Ravel |
| ⍪ | Table |
| ⌽⊖ | Reverse, Rotate |
| ⍴ | Reshape |
| ⊃ | Disclose, Pick |
| ⍉ | Transpose (Monadic and Dyadic) |
| /⌿ | Replicate |
| \⍀ | Expand |
| ⌷ | Index |
| ∊ | Enlist (⎕ML≥1) |
Note: Mix and Split (monadic ↑ and ↓), Type (monadic ∊ when ⎕ML<1) and Membership (dyadic ∊) may not be used in the selection expression.
A←'HELLO' ((A∊'AEIOU')/A)←'*' A H*LL* Z←3 4⍴⍳12 (5↑,Z)←0 Z 0 0 0 0 0 6 7 8 9 10 11 12
MAT←3 3⍴⍳9
(1 1⍉MAT)←0
MAT
0 2 3
4 0 6
7 8 0
⎕ML←1⍝ so ∊ is Enlist
names←'Andy' 'Karen' 'Liam'
(('a'=∊names)/∊names)←'*'
names
Andy K*ren Li*m
The functions listed in the table above may also be used with the Each Operator ¨.
A←'HELLO' 'WORLD'
(2↑¨A)←'*'
A
**LLO **RLD
A←'HELLO' 'WORLD'
((A='O')/¨A)←'*'
A
HELL* W*RLD
A←'HELLO' 'WORLD'
((A∊¨⊂'LO')/¨A)←'*'
A
HE*** W*R*D
Bracket indexing may also be applied to the expression on the left of the assignment arrow.
MAT←4 3⍴'Hello' 'World'
(¯2↑¨MAT[;1 3])←'$'
MAT
Hel$$ World Hel$$
Wor$$ Hello Wor$$
Hel$$ World Hel$$
Wor$$ Hello Wor$$