2. Index-Of Selfie
Index
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x⍳x
((⍳≢x)=x⍳x)⌿x
nub (unique)
(x⍳x)∘.=(x⍳y)
an efficient computation for
x∧.=⍉y
for matrices
x
and
y
(x⍳x)∘.=(x⍳y)
an efficient computation for
x∘.≡y
for non-simple vector
x
(x⍳x) f⌸ y
equivalent to
x f⌸ y