Dyalog Idioms
CHEAT SHEET
Dyalog v15.0
Idioms
Key to the types and ranks of the arguments in the idioms:
Type
Description
Rank
Description
C
Character
S
Scalar or single item vector
B
Boolean
V
Vector
N
Numeric
M
Matrix
P
Nested
A
Array of any rank
X
any type
The idioms described below must be entered precisely as shown to be recognised.
Idiom
Description
⍴⍴XA
The rank of XA (returned as a one-element vector)
≢⍴XA
The rank of XA (returned as a scalar)
BV/⍳NS
The subset of
NS
corresponding to the 1s in
BV
BV/⍳⍴XV
The positions in XV corresponding to the 1s in BV
NA⊃¨⊂XV
The subset of XV in the index positions defined by NA (equivalent to
XV[NA])
XA1{}XA2
XA1 and XA2 are ignored (no result produced)
XA1{⍺}XA2
XA1 (XA2 is ignored)
XA1{⍵}XA2
XA2 (XA1 is ignored)
XA1{⍺ ⍵}XA2
XA1 and XA2 as a two item vector (XA1 XA2)
{0}XA
0 irrespective of XA
{0}¨XA
0 corresponding to each item of XA
,/PV
The enclose of the items of PV catenated along their last axes
⍪/PV
The enclose of the items of PV catenated along their first axes
⊃⌽XA
The item in the top right of
XA
(
⎕ML<2
)
↑⌽XA
The item in the top right of XA (⎕ML≥2)
⊃⌽,XA
The item in the bottom right of XA (⎕ML<2)
↑⌽,XA
The item in the bottom right of XA (⎕ML≥2)
0=⍴XV
1 if XV has a shape of zero, 0 otherwise
0=⍴⍴XA
1 if XA has a rank of zero (scalar), 0 otherwise
0=≡XA
1 if XA has a depth of zero (simple scalar), 0 otherwise
XM1{(↓⍺)⍳↓⍵}XM2
A simple vector comprising as many items as there are rows in
XM2
,
where each item is the number of the first row in XM1 that matches
each row in XM2.
↓⍉↑PV
A nested vector comprising vectors that each correspond to a
position in the original vectors of PV – the first vector contains the
first item from each vector in PV, padded to be the same length as
the largest vector, and so on (⎕ML<2)
↓⍉⊃PV
A nested vector comprising vectors that each correspond to a
position in the original vectors of PV – the first vector contains the
first item from each vector in PV, padded to be the same length as
the largest vector, and so on (
⎕ML≥2
)
^\' '=CA
A Boolean mask indicating the leading blank spaces in each row of CA
+/^\' '=CA
The number of leading blank spaces in each row of CA
+/^\BA
The number of leading 1s in each row of
BA
{(∨\' '≠⍵)/⍵}CV
CV without any leading blank spaces
{(+/^\' '=⍵)↓⍵}CV
CV without any leading blank spaces
~∘' '¨↓CA
A nested vector comprising simple character vectors constructed
