They're used to guarantee that the functions needed by an algorithm are correctly defined. For instance, index_adjency_list requires vertices(g), out_edges(g,u) and others be defined, the underlying vertices(g) range is a random_access_range, the underlying out_edges(g,u) is a forward_range, etc.


________________________________
From: SG19 <sg19-bounces_at_[hidden]> on behalf of Vinnie Falco via SG19 <sg19_at_[hidden]>
Sent: Wednesday, June 17, 2026 5:11 PM
To: sg19_at_[hidden] <sg19_at_[hidden]>
Cc: Vinnie Falco <vinnie.falco_at_[hidden]>
Subject: [isocpp-sg19] Standardizing Graph concepts


EXTERNAL

Why do Graph concepts need to be in the standard library? Is there evidence of a coordination problem that is not currently being solved?

Thanks