libtlafmt 0.4.1

A formatter library for TLA+ specs, core of tlafmt
Documentation 
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---
source: libtlafmt/tests/format.rs
expression: output
input_file: libtlafmt/tests/corpus/SlidingPuzzles.tla
---
---------------------------- MODULE SlidingPuzzles -----------------------------
EXTENDS Integers

VARIABLE board

W == 4 H == 5
Pos == (0..W - 1) \X (0..H - 1)
Piece == SUBSET Pos

Klotski == {{<< 0, 0 >>, << 0, 1 >>},
    {<< 1, 0 >>, << 2, 0 >>, << 1, 1 >>, << 2, 1 >>},
    {<< 3, 0 >>, << 3, 1 >>}, {<< 0, 2 >>, << 0, 3 >>},
    {<< 1, 2 >>, << 2, 2 >>}, {<< 3, 2 >>, << 3, 3 >>},
    {<< 1, 3 >>}, {<< 2, 3 >>}, {<< 0, 4 >>}, {<< 3, 4 >>}}

KlotskiGoal == {<< 1, 3 >>, << 1, 4 >>, << 2, 3 >>, << 2, 4 >>} \notin board

ChooseOne(S, P(_) ) == CHOOSE x \in S: P(x) /\ \A y \in S: P(y) => y = x

TypeOK == board \in SUBSET Piece

(***************************************************************************)
(* Given a position and a set of empty positions return a set of           *)
(* appropriately filtered von Neumann neighborhood points                  *)
(***************************************************************************)
dir(p, es) == LET dir == {<< 1, 0 >>, << 0, 1 >>, << - 1, 0 >>, << 0, - 1 >>}
    IN {d \in dir:
        /\ << p[1] + d[1], p[2] + d[2] >> \in Pos
        /\ << p[1] + d[1], p[2] + d[2] >> \notin es}

(***************************************************************************)
(* Given a position and a unit translation vector return a pair of         *)
(* pieces, before and after translation in opposite this vector direction  *)
(***************************************************************************)
move(p, d) == LET s == << p[1] + d[1], p[2] + d[2] >>
        pc == ChooseOne(board, LAMBDA pc : s \in pc )
    IN << pc, {<< q[1] - d[1], q[2] - d[2] >>: q \in pc} >>

(***************************************************************************)
(* Given specific free position and a set of all free positions return     *)
(* a set of boards updated by moving appropriate pieces to that            *)
(* free position                                                           *)
(***************************************************************************)
update(e, es) == LET dirs == dir(e, es)
        moved == {move(e, d): d \in dirs}
        free == { <<pc, m>> \in moved:
            /\ m \intersect (UNION (board \ {pc})) = {}
            /\ \A p \in m: p \in Pos}
    IN {(board \ {pc}) \union {m}: <<pc, m>> \in free}

Init == board = Klotski

Next == LET empty == Pos \ UNION board
    IN \E e \in empty: board' \in update(e, empty)

================================================================================