Chankan: Difference between revisions

Chankan
Type	Yaku
Kanji	搶槓
English	Robbing a kan
Value	1 han
Speed	Dependent
Difficulty	Very hard

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Revision as of 17:21, 24 March 2024

Chankan 「搶槓」 is a standard yaku dependent on an opponent's kan. When an opponent calls to upgrade a minkou (triple called via pon) to a shominkan (added kan), a player in tenpai for that tile may call ron, gaining the yaku of chankan.

Development

Chankan example, where the player declared ron on 1-pin and all four are shown as a kan.

Known in English as "robbing a kan", chankan occurs when a player is in tenpai for a tile used to upgrade a pon into an added kan. Any tenpai hand works for chankan, even if the hand is otherwise yakuless. The other two types of kan can never be used for this yaku.

In almost all cases, players cannot ron off an ankan (closed kan). The notable exception is with a kokushi tenpai hand. For kokushi alone, the last tile needed for the yakuman may be won from an opponent's ankan. However, in some rules, kokushi cannot win from ankans.
It is impossible to ron off an Daiminkan (open kan). The call for ron takes precedence over the call for kan. Either a discarded tile is used for ron, or it is used to complete a kan. If the ron call is skipped, you cannot retroactively ron after the kan is made.

In other words, an opponent must call pon before your hand wins, then draw the fourth copy of that tile, then call the added kan. An opponent must have all four copies of a tile in their hand to call added kan. Therefore, chankan becomes impossible if you are holding any copy of that tile (because then the opponent cannot gain that tile for their kan).

Chankan interrupts the call for kan. This means that kan dora is not revealed after chankan, and denies the opponent's rinshan draw/

Machi

Main article: Machi

As mentioned above, in order to obtain chankan, it is impossible to have a copy of the given winning tile in your hand. Therefore, waits involving shanpon or tanki are impossible. If you hold a tile in your hand, the opponent cannot make an added kan, making it impossible to chankan with that tile.

So, when it comes to machi (wait patterns), only three basic types can be used: penchan, kanchan, and ryanmen. These are all waits to complete a sequence.

In the case for kokushi musou, the hand is tenpai for kokushi with one of the 13-tile types already paired; and it is waiting for the last tile type for completion. An exception to kan calls involving ankan (closed kan) is made.

Furiten

Chankan can only happen when a player calls pon. Therefore, there is at least one player who will be in furiten for chankan, and that is the player who was used to complete the original pon call.

Limitation

When a player is in tenpai for suukantsu, some rule variations allow invoking a fifth kan to cause a draw. If a fifth kan is allowed in this way, chankan may not apply - the game ends before a chankan can happen.

Compatibility

Main article: Yaku compatibility

^ Ippatsu requires riichi to be of any use.

	RCH	DRI	IPP	SMO	TAN	PFU	IPK	ITT	YAK	SDJ	SDO	TOI	SNA	SNK	CHA	JUN	RPK	SSG	HRO	HON	CHN	CHI	RIN	HAI	HOU	CHK
CHK

Excluding kokushi musou, chankan requires at least one sequence, because waits to complete a pair (tanki) or triplet (shanpon) would be impossible. This excludes toitoi, chiitoitsu, and honroutou. Ryanpeikou is also not allowed, due to the tile requirement. A ryanpeikou tenpai would require at least one copy of the winning tile, which prevents the other players from calling kan.

As for rinshan, haitei, houtei, and mentsumo, it is physically impossible to combine any of these four with chankan. Rinshan, mentsumo, and haitei require a win by self draw, while chankan is always won with ron. In the case of houtei, a player is not allowed to call kan if there are no tiles left in the live wall, so a chankan cannot be the last discard.

Ippatsu

The ippatsu yaku is normally interrupted by a kan call. To call chankan, the opposing player had already called for kan. However, ippatsu is still not interrupted because the whole kan process has not been completed. The entire kan process includes the kan call itself, plus the rinshan draw and the discard afterwards. The chankan win occurs in the middle of that process. So, it is allowable to score both ippatsu and chankan at the same time.

Double Riichi

Chankan requires an added kan, which itself requires a pon. This invalidates double riichi for any regular hand:

If a pon is made before the riichi call, double riichi is negated.
If the pon call happens after the riichi call, then the double riichi player must have declined their winning tile, invoking furiten. Since chankan can only be won off ron, furiten makes this yaku impossible.

However, an exception exists with kokushi musou. Depending on rule variation, kokushi may be won off a closed kan, which does not require a previous pon call. Therefore, in order to win with double riichi + chankan, it must also have kokushi. Since this would be a yakuman hand, neither double riichi or chankan would actually be scored.

Kokushi musou variation

If the rules allow, a special case for kokushi musou exists. When a kokushi hand is in tenpai, it may win if an opponent calls a closed kan for the tile you are winning for. Thus, ron may be declared, invoking this special rule. This is the only case where a tile may be taken from an closed kan.

However, this particular rule may be subject to variation, which may or may not allow this play to occur.

External links

搶槓

Chankan in Japanese Wikipedia

@@ Line 11: / Line 11: @@
 * [http://tenhou.net/0/?log=2015032605gm-0089-0000-70f97ed2&tw=0 Chankan baiman]
 }}
-'''Chankan''' {{kana|搶槓}} is a standard yaku.  It is dependent on the usage of [[kan]], where a player may declare ron while a player calls to upgrade a [[koutsu|minkou]] (triple called via [[pon]]) to a [[Kan#Shominkan|shominkan]] (added kan).  In other words, if a player is tenpai for a tile used for that specific added kan, then the player may declare a win on that tile.
+'''Chankan''' {{kana|搶槓}} is a standard yaku dependent on an opponent's [[kan]]. When an opponent calls to upgrade a [[koutsu|minkou]] (triple called via [[pon]]) to a [[Kan#Shominkan|shominkan]] (added kan), a player in tenpai for that tile may call ron, gaining the yaku of chankan.
-In almost all cases, players are not allowed to call ron on an [[Kan#Ankan|ankan]] (closed kan). The notable exception involves a [[kokushi]] [[tenpai]] hand, where the last tile needed for the yakuman is called for an ankan.  However, the kokushi exception varies on the rules.  In [[Rule_variations#Kokushi_and_chankan|some rules]], it is disallowed outright.
+==Development==
-==Hand pattern==
 [[image:Chankan.png|250px|thumb|[http://tenhou.net/0/?log=2012112813gm-0009-7447-af4e435f&tw=2&ts=8 Chankan example], where the player declared ron on 1-pin and all four are shown as a kan.]]
+Known in English as "robbing a kan", chankan occurs when a player is in [[tenpai]] for a tile used to upgrade a [[pon]] into an added [[kan]]. Any tenpai hand works for chankan, even if the hand is otherwise yakuless. The other two types of kan can never be used for this yaku.
-Alternatively, this yaku may be referred to as "robbing a kan".  [[Tenpai]] for chankan must involve a hand, in which one of the [[machi|waiting tiles]] has been called as [[naki|pon]] by another player.  Any tenpai hand works for chankan, even if the hand is otherwise yakuless.  As long as the waiting tile has been called for [[naki|pon]] earlier and then the player calls for an added kan, this creates a time for a player to claim the added tile for a win.  Naturally, waits involving [[jihai|honor tiles]] do not work in this situation.
+*In almost all cases, players cannot ron off an [[ankan]] (closed kan). The notable exception is with a [[kokushi]] [[tenpai]] hand. For kokushi alone, the last tile needed for the yakuman may be won from an opponent's ankan. However, in [[Rule_variations#Kokushi_and_chankan|some rules]], kokushi cannot win from ankans.
+*It is impossible to ron off an [[Kan#Daiminkan|Daiminkan]] (open kan). The call for ron takes precedence over the call for kan. Either a discarded tile is used for ron, or it is used to complete a kan. If the ron call is skipped, you cannot retroactively ron after the kan is made.
-While the call for kan reveals additional [[dora]], in the form of kan-dora, the call for chankan interrupts the process for kan.  Therefore, additional dora is not revealed.
+In other words, an opponent must call [[pon]] before your hand wins, then draw the fourth copy of that tile, then call the added kan. An opponent must have all four copies of a tile in their hand to call added kan. Therefore, chankan becomes impossible if you are holding any copy of that tile (because then the opponent cannot gain that tile for their kan).
-===Limitation===
+Chankan interrupts the call for kan. This means that [[kan dora]] is not revealed after chankan, and denies the opponent's [[rinshan]] draw/
-When a player is in tenpai for [[suukantsu]], some [[rule variations]] allow invoking a fifth kan to cause a draw. If a fifth kan is allowed in this way, chankan may not apply - the game ends before a chankan can happen.
+===Machi===
-==Machi==
 {{main|Machi}}
+As mentioned above, in order to obtain chankan, it is impossible to have a copy of the given winning tile in your hand. Therefore, waits involving [[shanpon]] or [[tanki]] are impossible. If you hold a tile in your hand, the opponent cannot make an added kan, making it impossible to chankan with that tile.
-As defined, chankan can only be achieved when a [[minkou]] (open triplet) is upgraded to a ''shouminkan''.  In other words, a player had called pon earlier and then drew the 4th tile, for the kan.  If another player is tenpai for that tile, then the player may declare ron.  To some degree, the added kan may be viewed as a discard in this case.
+So, when it comes to [[machi]] (wait patterns), only three basic types can be used: [[penchan]], [[kanchan]], and [[ryanmen]]. These are all waits to complete a [[shuntsu|sequence]].
-So, when it comes to [[machi]] (wait patterns), only three basic types can be used for chankan: [[penchan]], [[kanchan]], and [[ryanmen]]. To achieve chankan, all four copies of a tile would have needed to been in another player's hand. Therefore, a hand winning with chankan must not have any other copies of the winning tile. This forbids tile patterns involving [[shanpon]] and [[tanki]], as these waits require another copy of the tile.
 In the case for [[kokushi musou]], the hand is tenpai for kokushi with one of the 13-tile types already paired; and it is waiting for the last tile type for completion.  An exception to kan calls involving [[ankan]] (closed kan) is made.
 ===Furiten===
-Under any possible instance of chankan, one player is barred from calling ron and awarded this yaku due to [[furiten]].  The initial tile discard was granted for the open call for pon.
+Chankan can only happen when a player calls pon. Therefore, there is at least one player who will be in [[furiten]] for chankan, and that is the player who was used to complete the original pon call.
+===Limitation===
+When a player is in tenpai for [[suukantsu]], some [[rule variations]] allow invoking a fifth kan to cause a draw. If a fifth kan is allowed in this way, chankan may not apply - the game ends before a chankan can happen.
 == Compatibility ==
@@ Line 45: / Line 45: @@
 Excluding kokushi musou, chankan requires at least one sequence, because waits to complete a pair (tanki) or triplet (shanpon) would be impossible. This excludes [[toitoi]], [[chiitoitsu]], and [[honroutou]]. [[Ryanpeikou]] is also not allowed, due to the tile requirement. A ryanpeikou tenpai would require at least one copy of the winning tile, which prevents the other players from calling kan.
-As for [[rinshan]], [[haitei]], [[houtei]], and [[mentsumo]], it is physicially impossible to combine any of these four with chankan. Rinshan, mentsumo, and haitei require a win by self draw, while chankan is always won with ron. In the case of houtei, a player is not allowed to call kan if there are no tiles left in the live wall, so a chankan cannot be the last discard.
+As for [[rinshan]], [[haitei]], [[houtei]], and [[mentsumo]], it is physically impossible to combine any of these four with chankan. Rinshan, mentsumo, and haitei require a win by self draw, while chankan is always won with ron. In the case of houtei, a player is not allowed to call kan if there are no tiles left in the live wall, so a chankan cannot be the last discard.
 === Ippatsu ===
-The [[ippatsu]] yaku is normally interrupted by a kan call.  To call chankan, the opposing player had already called for kan.  However, ippatsu is still not interrupted because the whole kan process has not been completed.  The entire kan process includes the kan call itself, plus the rinshan draw and the discard afterwards.  The chankan win occurs in the middle of that process.  So, it is allowable to score both ippatsu and chankan at the same time.
+The [[ippatsu]] yaku is normally interrupted by a kan call. To call chankan, the opposing player had already called for kan.  However, ippatsu is still not interrupted because the whole kan process has not been completed.  The entire kan process includes the kan call itself, plus the rinshan draw and the discard afterwards.  The chankan win occurs in the middle of that process.  So, it is allowable to score both ippatsu and chankan at the same time.
 === Double Riichi ===
@@ Line 58: / Line 58: @@
 However, an exception exists with [[kokushi musou]]. Depending on [[Kokushi_musou#Chankan_rule_variation|rule variation]], kokushi may be won off a [[ankan|closed kan]], which does not require a previous pon call. Therefore, in order to win with double riichi + chankan, it must also have kokushi. Since this would be a yakuman hand, neither double riichi or chankan would actually be scored.
-== Special cases ==
+== Kokushi musou variation ==
 [[Image:Kokushi deny.png|thumb|right|250px|Case where a [[kan|closed kan]] was declared during a [http://tenhou.net/0/?log=2018041311gm-000b-7447-e286a4e6&tw=2&ts=6 kokushi tenpai].]]
+If the rules allow, a special case for [[kokushi musou]] exists. When a kokushi hand is in tenpai, it may win if an opponent calls a closed kan for the tile you are winning for. Thus, ron may be declared, invoking this special rule. This is the only case where a tile may be taken from an closed kan.
-=== Rinshan kaihou ===
+However, this particular rule may be [[Yaku_variations#Kokushi_and_chankan|subject to variation]], which may or may not allow this play to occur.
-Given the procedure for kan, the chankan takes precedence over [[rinshan kaihou]].  Here, the call for a chankan win denies even the drawing of the rinshan tile.  Therefore, even the chance for rinshan kaihou is denied.
-=== Kokushi musou ===
-If the rules allow, a special case for [[kokushi musou]] exists.  This involves a kokushi tenpai hand, where the final tile may be completed with an opponent calling [[kan]] with a closed kan using all four of that particular winning tile.  Thus, ron may be declared in that instance, involving the special chankan rule.  This is the only case where a tile may be taken from an closed kan.  However, this particular rule may be [[Yaku_variations#Kokushi_and_chankan|subject to variation]], which may or may not allow the play to occur.
 ==External links==