Index
A digit points to its own position in the stated row or column axis. The digit in the pointed cell gives the position of the original cell.
Parameters
| Parameter | Meaning | Default |
|---|---|---|
| strips | The marked cells in each straight strip. | No authored strips. |
| axis | The indexing direction: row or column. | Required. |
| cells | The marked cells, for example r1c1-r1c2-r2c2. | Required. |
Maths
Class: first-order.
The shared predicates define the notation and every named predicate.
∀c∈cells: (axis="column" → 1<=D(c)<=cols ∧ D(boardCell(row(c),D(c)-1))=col(c)+1) ∧ (axis="row" → 1<=D(c)<=rows ∧ D(boardCell(D(c)-1,col(c)))=row(c)+1)
For column axis, each marked digit names a one-based column in its row; that target contains the marked cell’s column number. Row axis exchanges rows and columns. The named position must be within the board.
Example
---
format: open-rules
title: Index example
setter: Example
source: ""
case: ""
library: https://rules.sudoku-sleuth.com/
status: read
---
```rules
sudoku 9x9
index r1c1 axis "column"
```
Satisfies the rule: r1c1=2, r1c2=1. The 2 points to the second cell, which contains the original position 1.
Breaks the rule: r1c1=2, r1c2=3. The pointed cell contains 3 instead of position 1.