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new 80c06354ae Correct fold() callout for list vs map seed with addAll
80c06354ae is described below
commit 80c06354aeb79c183d20da22f4eff0ff4e81fe48
Author: Stephen Mallette <[email protected]>
AuthorDate: Thu Jul 23 17:59:21 2026 +0000
Correct fold() callout for list vs map seed with addAll
The Fold Step reference example annotated
g.inject(["a":1],["b":2]).fold([], addAll)
as merging Map instances with last-writer-wins key replacement. With a list
seed,
addAll actually collects the incoming maps into a list ([[a:1],[b:2]]) with
no
merging. Rewrite that callout to describe the list-seed behavior accurately
and add
a companion map-seed example, g.inject(["a":1],["b":2]).fold([:], addAll),
whose
callout describes the real putAll merge ([a:1,b:2], last occurrence wins).
Make the
seed-type dependence of addAll explicit.
Assisted-by: Kiro:claude-opus-4.8
---
docs/src/reference/the-traversal.asciidoc | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/docs/src/reference/the-traversal.asciidoc
b/docs/src/reference/the-traversal.asciidoc
index 94606c60f7..36e66f67ca 100644
--- a/docs/src/reference/the-traversal.asciidoc
+++ b/docs/src/reference/the-traversal.asciidoc
@@ -2181,6 +2181,7 @@ g.V().values('age').fold(0) {a,b -> a + b} <4>
g.V().values('age').fold(0, sum) <5>
g.V().values('age').sum() <6>
g.inject(["a":1],["b":2]).fold([], addAll) <7>
+g.inject(["a":1],["b":2]).fold([:], addAll) <8>
----
<1> A parameterless `fold()` will aggregate all the objects into a list and
then emit the list.
@@ -2189,7 +2190,8 @@ g.inject(["a":1],["b":2]).fold([], addAll) <7>
<4> What is the total age of the people in the graph?
<5> The same as before, but using a built-in bi-function.
<6> The same as before, but using the <<sum-step,`sum()`-step>>.
-<7> A mechanism for merging `Map` instances. If a key occurs in more than a
single `Map`, the later occurrence will replace the earlier.
+<7> With a list seed (`[]`), `addAll` collects the incoming `Map` traversers
into a list, yielding `[[a:1],[b:2]]`. The two maps are gathered as separate
elements, so they are not merged and no key replacement occurs.
+<8> With a map seed (`[:]`), `addAll` instead merges the incoming maps into a
single `Map` (via `putAll`), yielding `[a:1,b:2]`. If a key occurs in more than
a single `Map`, the later occurrence replaces the earlier. The behavior of
`addAll` therefore depends on the seed type: a list seed collects the elements
into a list, while a map seed merges the maps.
*Additional References*
