Was checking the subject page and noted a dangling phrase (see underlined below):
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https://code.jsoftware.com/wiki/Vocabulary/icapdot
More Information
1. I. y is the same as (y # i. # y)
2. If an atom of y is greater than 1, the corresponding index is repeated.
3. I.^:_1 (the obverse of I.) gives the frequencies of the atoms of y, which must be nonnegative. The atom with index i gives the number of occurrences of i in y.
follows from 1.
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Maybe it was intended as a note - not sure.