(* Title: Plane1.thy
ID: $Id: Plane1.thy,v 1.1 2006/01/04 13:43:59 nipkow Exp $
Author: Gertrud Bauer, Tobias Nipkow
Fixing a single face and vertex in each refinement step.
*)
theory Plane1
imports Plane
begin
text{* This is an optimized definition of plane graphs and the one we
adopt as our point of reference. In every step only one fixed nonfinal
face (the smallest one) and one edge in that face are picked. *}
constdefs minimalFace:: "face list => face"
"minimalFace ≡ minimal (length o vertices)"
constdefs minimalVertex :: "graph => face => vertex"
"minimalVertex g f ≡ minimal (height g) (vertices f)"
constdefs next_plane :: "nat => graph => graph list" ("next'_plane_{_}")
"next_plane_{p} g ≡
let fs = nonFinals g in
if fs = [] then []
else let f = minimalFace fs; v = minimalVertex g f in
\<Squnion>_{i∈[3..maxGon p]} generatePolygon i v f g"
constdefs
PlaneGraphsP :: "nat => graph set" ("PlaneGraphs_{_}")
"PlaneGraphs_{p} ≡ {g. Seed_{p} [next_plane_{p}]->* g ∧ final g}"
PlaneGraphs :: "graph set"
"PlaneGraphs ≡ \<Union>p. PlaneGraphs_{p}"
end