From OpenCog

The AccumulateLink is a type of FunctionLink that can be used to reduce vectors to scalars, by summing all of the vector components.

For example:

(Accumulate (Number 1 2 3))

will return

(NumberNode 6)

This works with formulas, so that the following works as expected:

(cog-set-value! (Concept "abc") (Predicate "key") (FloatValue 0.1 0.2 0.3))
(cog-execute! (Accumulate (ValueOf (Concept "abc") (Predicate "key"))))

will return

 (FloatValue 0.6)

See also