[TINKERPOP-1849] Provide a way to fold() with an index

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.3.0
• Fix Version/s: 3.4.0
• Component/s: process
• Assignee: Daniel Kuppitz
• Reporter: Stephen Mallette
• Created: 06/Dec/17 16:47
• Updated: 17/Dec/18 17:14
• Resolved: 17/Dec/18 17:14

Description

In Groovy you can call withIndex() to generate output like this:

gremlin> g.V().fold().next().withIndex()
==>[v[1],0]
==>[v[2],1]
==>[v[3],2]
==>[v[4],3]
==>[v[5],4]
==>[v[6],5]

We can currently simulate this with Gremlin via:

gremlin> g.V().project("a","b").by().by(select("x").count(local)).store("x").map(union(select('a'), select('b')).fold()).fold().next()
==>[v[1],0]
==>[v[2],1]
==>[v[3],2]
==>[v[4],3]
==>[v[5],4]
==>[v[6],5]

but it's not easy to follow, efficient, or potentially foolproof. Perhaps we can add an option to fold() that would take an enum of "fold operators".

Issue Links

• links to: GitHub Pull Request #1011