iterfolder is a package for go1.22 (using the "rangefunc" experiment) or higher that takes an iterator which is a composite of three types and "folds" left hand items of common value. This might be useful, for example, for putting the results of a sql "domain aggregate" query returning rows coerced to compound struct of structs (e.g. rows of `{person}{car}{ticket}`) into a tiered iterator which can be used as follows: Note that the input iterator should be pre-sorted and that duplicate "rows" are not squashed. Note that as of July 2024, Go templates do not yet support iterating over an iter.Seq. See https://go.dev/issue/66107. For more information about the rangefunc experiment, see https://go.dev/wiki/RangefuncExperiment.