Symbol Zilde
From NARS2000
⍬ — Represents an empty numeric vector or zero plus tilde (hence zilde) — Keystroke Alt + Shift + } — Character
Usage
⌊/⍬
∞
⌈/⍬
¯∞
Symbolically zero or 0 represents number while tilde or ∼ represents not. Together the overstrike zilde symbol or ⍬ means not a number, i.e. empty numeric vector. APL frequently uses overstrike characters in dualcombined meaning, thus ⍞ which is ⎕ or prompt and the single quote symbol yielding prompt for string or character input versus ⎕ or prompt for numeric input.
Example
The above examples for infinity and negative infinity correctly run in NARS2000. In theory ONLY  ⍬ would be hypothetically equivalent to ⍳0 or 0⍴N (where N is any number) since zilde or ⍬ represents an empty numeric vector.
See Also
See Also
System Commands
System Variables and Functions
Operators
Keyboard
A+S
⍪
≡
≢
⍒
⍋
⌽
⍉
⊖
⍟
⍱
⍲
⍠
⌹
Alt
⋄
¨
¯
<
≤
∅
≥
>
≠
∨
∧
×
÷
Sh
~
!
@
#
$
%
^
&
*
(
)
_
+
Key
`
1
2
3
4
5
6
7
8
9
0

=
A+S
⍷
√
⍨
⍸
⍥
⍣
⍞
⍬
⊣
Alt
?
⍵
∊
⍴
§
↑
↓
⍳
○
π
←
→
⊢
Sh
Q
W
E
R
T
Y
U
I
O
P
{
}

Key
q
w
e
r
t
y
u
i
o
p
[
]
\
A+S
∫
∂
⌻
⍢
⍙
⍤
⍫
⌷
Alt
⍺
⌈
⌊
∞
∇
∆
∘
‼
⎕
⍎
⍕
Sh
A
S
D
F
G
H
J
K
L
:
"
Key
a
s
d
f
g
h
j
k
l
;
'
A+S
⊆
⊇
χ
⍡
⍭
⊙
Alt
⊂
⊃
∩
∪
⊥
⊤
⍦
⍝
⍀
⌿
Sh
Z
X
C
V
B
N
M
<
>
?
Key
z
x
c
v
b
n
m
,
.
/
NARS 2000 Lang
Tool
Bar
←
→
+

×
÷
*
⍟
⌹
○
!
?
√

⌈
⌊
⊥
⊤
⊣
⊢
≡
≢
<
≤
=
≥
>
≠
∨
∧
⍱
⍲
↑
↓
⊂
⊃
⌷
⍋
⍒
⍳
∊
⍸
⍷
∪
∩
⊆
⊇
~
§
π
..
,
⍪
⍴
⌽
⊖
⍉
/
\
⌿
⍀
⊙
¨
⍨
⍤
⍣
⍡
⍥
⍦
.
∘
⍠
‼
⌻
∂
∫
⍞
⎕
⍎
⍕
⋄
⍝
∇
∆
⍙
_
⍺
⍵
¯
⍬
∞
Second Row
i j k
i j k l
g
p
r
v
x
∞
⌈/⍬
¯∞
Tool
Bar