Other rules

This page covers the remaining rule families (6.13), vendor rules (6.15), what is not a rule (6.16) and reserved names (6.17).

6.13 Other families

{"type": "contains", "digits": [1, 9], "cells": ["r1c1", "r1c2", "r2c1", "r2c2"]}
{"type": "appears", "source": "r5c5", "cells": ["r5c6", "r5c7", "r5c8", "r5c9"]}
{"type": "clone", "regions": [["r1c1", "r1c2"], ["r9c8", "r9c9"]]}
{"type": "isomorphic", "regions": [["r1c1", "…81 cells…"], ["r1c11", "…81 cells…"]]}
{"type": "count", "each": 2, "cells": ["r1c1", "…"]}
{"type": "count", "kind": "circles", "cells": ["r1c1", "r4c7"]}
{"type": "distinct_count", "value": 2, "side": "top", "cells": ["r1c2", "r2c3", "r3c4"]}
{"type": "global_entropy"}
{"type": "equal_sum", "segments": [["r1c1", "r1c2"], ["r2c3"]]}
{"type": "vudoku", "cells": ["r2c2", "r1c2", "r2c3"]}

type	Meaning	Drawing
contains	Every listed digit (a multiset) appears among cells at least as often as it is listed. On a 2×2 block it is the quadruple clue.
appears	The digit in source appears in at least one of cells (an in-cell arrow whose digit occurs again along its ray).
clone	≥ 2 equal-sized ordered regions; corresponding cells hold equal digits.
isomorphic	2 ordered regions (twins): one fixed relabelling of the digits maps every cell of the first region to the corresponding cell of the second.
count	each k: every digit appears exactly k times among cells (Double Sudoku rows). Or counts [[digit, times], …]: those digits appear exactly that often. Kind circles: a digit that appears among the cells appears exactly as many times as its own value. The cells of an each or counts rule MUST NOT also form a house (their digits repeat: a Double Sudoku row is a count, not a row); counting circles may sit on any cells.
distinct_count	Exactly value different digits among cells. With side it is an outside clue (ordered cells).
global_entropy	Every 2×2 window of existing cells holds a low, a middle and a high digit (thirds of 1..D; D divisible by 3).
equal_sum	Every segment (a cell set) has the same sum. For lines, use the line kinds zipper, region_sum, double_arrow.
vudoku	cells = [vertex, arm, arm], usually an L of three cells (the arms beside the vertex): the vertex digit is the sum or the difference of the two arm digits.

6.15 Vendor rules

{"type": "com.example:my_rule", …}: must-understand like every other rule; a reader that does not implement it refuses the file.

6.16 What is not a rule

Variant names (Argyle, Windoku, …) are not rules: they are meta.type only. Colours, fonts and artwork are style and decorations only.

6.17 Reserved

• "type": "custom": reserved for a future rule language (rules defined in the file itself); every format_version 1 reader refuses it with a message saying so. Until then, a mechanic without a rule family cannot be written in the format.
• "type": "table" and the operator allowed (explicit lists of allowed digit tuples): reserved and refused. Such lists make files large and cannot be drawn; the custom rule type is meant to replace them.
• digits as an object ({"values": [0, …, 8], "symbols": {…}}, with an empty sentinel) for digit sets other than 1..D, and digit-selection puzzles: reserved; refused in format_version 1.