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Include content only once

singleton(x, value = TRUE)

is.singleton(x)

Arguments

x A tag, text, HTML, or list.
value Whether the object should be a singleton.

Description

Use singleton to wrap contents (tag, text, HTML, or lists) that should be included in the generated document only once, yet may appear in the document-generating code more than once. Only the first appearance of the content (in document order) will be used.