Ilia Denisov
d70bd35470
Under PlayOptions.IgnoreCrossWords a play connected to the board through any perpendicular contact, even one forming a non-word, because connected() reused the standard rule's touchesPerpendicular test while cross-words were suppressed. That let an all-new word merely abut the board sideways and be accepted, and the generator, with relaxed cross-sets, offered such plays. Require the main word to run through an existing tile along the play direction when cross-words are ignored, and filter generated moves by the same predicate so generation agrees with ValidatePlayOpts. Standard rules are unchanged.
87 lines
3.1 KiB
Go
87 lines
3.1 KiB
Go
// Package scrabble is the public library: it builds a move generator over a dictionary
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// and a ruleset, generates every legal play for a position ranked by score, and scores
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// or validates arbitrary plays. The generator is the DAWG algorithm (Appel-Jacobson).
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package scrabble
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// Direction is the orientation of a play's main word.
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type Direction uint8
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const (
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// Horizontal is an across play (left to right along a row).
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Horizontal Direction = iota
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// Vertical is a down play (top to bottom along a column).
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Vertical
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)
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// String renders the direction for diagnostics.
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func (d Direction) String() string {
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if d == Vertical {
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return "vertical"
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}
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return "horizontal"
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}
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// Mode selects which orientations GenerateMoves produces. Russian "Эрудит" requires a
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// single orientation per turn, which OnlyHorizontal / OnlyVertical express.
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type Mode uint8
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const (
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// Both generates across plays (on the board) and down plays (on its transpose).
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Both Mode = iota
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// OnlyHorizontal generates across plays only.
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OnlyHorizontal
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// OnlyVertical generates down plays only.
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OnlyVertical
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)
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// Includes reports whether the mode produces plays in direction d.
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func (m Mode) Includes(d Direction) bool {
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switch m {
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case Both:
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return true
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case OnlyHorizontal:
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return d == Horizontal
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case OnlyVertical:
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return d == Vertical
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}
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return false
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}
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// Placement is a single newly-placed tile.
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type Placement struct {
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Row, Col int
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Letter byte // alphabet letter index
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Blank bool // placed from a blank tile, so it scores 0
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}
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// Word is a word formed by a play, with its location and score.
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type Word struct {
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Row, Col int // square of the word's first letter
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Dir Direction // orientation of the word
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Letters []byte // alphabet indices of the whole word (existing + new tiles)
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Blanks []bool // per letter: true if that tile is a blank (scores 0)
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Score int // the word's score, with premiums from newly-placed tiles
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}
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// Move is a complete legal play with a full scoring breakdown.
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type Move struct {
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Dir Direction // orientation of the main word
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Tiles []Placement // the newly-placed tiles, in main-word order
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Main Word // the main word formed along Dir
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Cross []Word // perpendicular words formed by the new tiles
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Bonus int // all-tiles (bingo) bonus included in Score, or 0
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Score int // total: Main.Score + Σ Cross.Score + Bonus
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}
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// PlayOptions tunes optional rule variations applied when evaluating, validating or
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// generating plays. The zero value is standard Scrabble.
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type PlayOptions struct {
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// IgnoreCrossWords makes a play's perpendicular cross-words irrelevant: they are not
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// formed, validated, scored or used to constrain move generation. It expresses the
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// "single word per turn" house rule, under which only the main word along the play
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// direction must be a valid word. That main word must still connect by running through
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// an existing tile along its line — a tile that only abuts the board perpendicular to
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// that line does not connect — and the first-move centre rule still applies.
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IgnoreCrossWords bool
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}
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