fact: Definition pmap n m := [map z1 z2 | [/\ in_pmap n z1, in_pmap n z2 & m z1 z2]].
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(path ssralg ssrint) fourcolor(real realplane realsyntax realprop) fourcolor(grid approx)