Slash Bar ⌿

Used as a Function

Monadic Slash Bar is not defined

Dyadic Slash Bar means

Replicate First (Compress First)

      mat
1  2  3  4
5  6  7  8
9 10 11 12

      1 0 2 ⌿ mat
1  2  3  4
9 10 11 12
9 10 11 12

Used as an Operator

Slash Bar is a Monadic operator with a Dyadic operand

Operator Slash Bar means

Reduce First, Reduce First N-Wise

      +⌿ mat
15 18 21 24

      2 +⌿ mat     ⍝ pair-wise
 6  8 10 12
14 16 18 20

Language Elements