miniapl

⌸ — Key

K f⌸Y groups major cells of Y by corresponding keys in K. Calls key f group; groups appear in first-occurrence order.

1 1 2{+/⍵}⌸10 20 30 ⍝ 30 30

f⌸Y uses Y as keys and their positions as values.

{≢⍵}⌸'banana'       ⍝ 1x 3x 2x

Keys use tolerant matching against first representatives. Results assemble with fill. Empty input calls f once for its prototype.

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