↦ — Range / To

Function. Keys: Alt-l. Ranks: 0 monadic, 0 0 dyadic

X↦Y counts from X to Y in steps of 1. It counts down when Y is less than X. Two characters count through the code points between them.

2↦5          ⍝ 2 3 4 5
5↦2          ⍝ 5 4 3 2
'a'↦'e'      ⍝ "abcde"

The last item is the last step that doesn’t pass Y. The number of steps counts as whole within comparison tolerance.

0.5↦3        ⍝ 0.5 1.5 2.5
0↦0.3÷0.1    ⍝ 0 1 2 3

Each item is X plus or minus an exact count: 0ₓ, 1ₓ, 2ₓ and so on. The result’s type therefore follows X. Y sets only how many items there are.

1ₓ↦5         ⍝ [1 2 3 4 5]ₓ
1↦5ₓ         ⍝ 1 2 3 4 5

↦N counts from 1 up to N, or from ¯1 down to N when N is negative. It has ⌊|N items. ↦0 is empty. The result’s type follows N.

↦4           ⍝ 1 2 3 4
↦¯3          ⍝ ¯1 ¯2 ¯3
↦0           ⍝ ⍬

On a vector, ↦ applies to each item, as Rank does. Fill pads the results to a common length.

↦2 3         ⍝ [1 2 0⋄1 2 3]

Errors

  • DOMAIN: a complex number, a character with a number, or an infinite end
  • LIMIT: more items than an array can hold