Map G : Graph α β to a Graph α' β with the same edge set
by applying a function f : α → α' to each vertex.
Edges between identified vertices become loops.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- Graph.«term_''ᴳ_» = Lean.ParserDescr.trailingNode `Graph.«term_''ᴳ_» 51 52 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol " ''ᴳ ") (Lean.ParserDescr.cat `term 52))
Instances For
To prove that H is an image of G, it suffices to show some set containments,
and mapping links in one direction.
IsContractClosed predicate #
Similar to how combining injecitivity and surjectivity gives a bijection,
IsContractClosed is one half of predicate that ensures that contract is sound.
IsContractClosed G φ C means that φ identifies the endpoints of every edge in C. So each fiber
of φ is a closed subgraph of G ↾ C.
Notice that each fiber may not be the components of G ↾ C. However, it is sometime useful to
use this half-predicate in proofs since it is well-behaved under subgraphs and subsets of C.
Under IsContractClosed, every edge in C becomes a loop after mapping.
A vertex-deletion-stable version: if e ∈ C and e survives deleting S from the mapped
graph, then e is a loop in ((φ ''ᴳ G) - S).
A tactic for providing the proof required in edgeMap in the case where the function
is known to be injective on the edge set.
Equations
- Graph.tacticEdgeMap_tac = Lean.ParserDescr.node `Graph.tacticEdgeMap_tac 1024 (Lean.ParserDescr.nonReservedSymbol "edgeMap_tac" false)
Instances For
The assumption hσ is needed for an edge-map to be well-defined without choice.
It holds in particular if InjOn σ E(G), and the autoParam will prove it if this is known.
simps doesn't play nice with the autoParam, so the simp lemms are proved manually.
Equations
- One or more equations did not get rendered due to their size.
Instances For
If φ and ψ are functions out of the vertex and edge sets respectively,
a sufficient condition for a graph H to be a map of G by φ and ψ.
This will only apply if φ and ψ give an isomorphism from G to H.
If φ and ψ are functions out of the vertex and edge sets respectively,
a sufficient condition for a graph H to be a map of G by φ and ψ.
This will only apply if φ and ψ give an isomorphism from G to H.