The three search functions are Index of (⊐), Progressive Index of (⊒), and Member of (∊). These are dyadic functions that search one argument ("searched-in") for major cells matching cells from the other ("searched-for"). For example, Index of returns, for each cell in 𝕩, the index of the first cell in 𝕨 that matches it.
| Name | for | in | Return | |
|---|---|---|---|---|
⊐ |
Index of | 𝕩 |
𝕨 |
Index of first match |
⊒ |
Progressive Index of | 𝕩 |
𝕨 |
Index of first unused match |
∊ |
Member of | 𝕨 |
𝕩 |
1 if found, 0 if not |
⍋⍒ |
Bins | 𝕩 |
𝕨 |
Predecessor index |
The searched-for argument is 𝕩 in Index-of functions (⊐⊒) and 𝕨 in Member of (∊). Bins Up and Down (⍋⍒) are ordering functions but follow the same pattern as Index-of. It's split into cells, but not necessarily major cells: instead, the cells used match the rank of a major cell of the other (searched-in) argument. In the most common case, when the searched-in argument is a list, 0-cells are used for the search (we might also say elements, as it gives the same result).
The result is always an array containing one number for each searched-for cell. For Index of and Member of, every result is computed independently; for Progressive Index of the result for a cell can depend on earlier cells, in index order.