Function opg::dfs::compose_elements

pub fn compose_elements(
    mono: &HashMap<String, HashSet<String>>, 
    con: &HashMap<String, HashSet<String>>
) -> HashMap<String, HashSet<String>>

Compose the elements from mono and con.

Input

mono the direct relation for terminals and non-terminals.

con the inherit relation between non-terminals.

Return

A Hashmap of VT.

Example

let firstvt = dfs::compose_elements(&firstvtmono, &firstvtcon);

Principles

By create new Dfs struct and call dfs() function, the following process is proceed:

• The first DFS: dfs_merge() will use a union-find way to detect the non-terminals like S1 subseteq S2 subseteq ... subseteq Sn subseteq S1 and make them in the same category.
• The second DFS: dfs_conn() will make connections between the categories detected in the previous stage. After this stage, there will be no loop in the dependency graph, i.e., a tree.
• The third DFS: dfs_map() will perform DFS on every non-terminals in the category relation tree to get the corresponding VT set for the non-terminal.