tokens_split: Split tokens by a separator pattern
In koheiw/quanteda.core: Quantitative Analysis of Textual Data

Replaces tokens by multiple replacements consisting of elements split by a separator pattern, with the option of retaining the separator. This function effectively reverses the operation of tokens_compound().

tokens_split(
  x,
  separator = " ",
  valuetype = c("fixed", "regex"),
  remove_separator = TRUE
)

`x`	a tokens object
`separator`	a single-character pattern match by which tokens are separated
`valuetype`	the type of pattern matching: `"glob"` for "glob"-style wildcard expressions; `"regex"` for regular expressions; or `"fixed"` for exact matching. See valuetype for details.
`remove_separator`	if `TRUE`, remove separator from new tokens

# undo tokens_compound()
toks1 <- tokens("pork barrel is an idiomatic multi-word expression")
tokens_compound(toks1, phrase("pork barrel"))
tokens_compound(toks1, phrase("pork barrel")) %>%
    tokens_split(separator = "_")
    
# similar to tokens(x, remove_hyphen = TRUE) but post-tokenization 
toks2 <- tokens("UK-EU negotiation is not going anywhere as of 2018-12-24.")
tokens_split(toks2, separator = "-", remove_separator = FALSE)