Dear Rui,

On 10/18/2023 8:45 PM, Rui Barradas wrote:
split_chem_elements <- function(x, rm.digits = TRUE) {
  regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
  if(rm.digits) {
    stringr::str_replace_all(mol, regex, "#") |>
      strsplit("#|[[:digit:]]") |>
      lapply(\(x) x[nchar(x) > 0L])
  } else {
    strsplit(x, regex, perl = TRUE)
  }
}

split.symbol.character = function(x, rm.digits = TRUE) {
  # Perl is partly broken in R 4.3, but this works:
  regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
  s <- strsplit(x, regex, perl = TRUE)
  if(rm.digits) {
    s <- lapply(s, \(x) x[grep("[[:digit:]]+", x, invert = TRUE)])
  }
  s
}

You have a glitch (mol is hardcoded) in the code of the first function. The times are similar, after correcting for that glitch.

Note:
- grep("[[:digit:]]", ...) behaves almost twice as slow as grep("[0-9]", ...)!
- corrected results below;

Sincerely,

Leonard
#######

split_chem_elements <- function(x, rm.digits = TRUE) {
  regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
  if(rm.digits) {
    stringr::str_replace_all(x, regex, "#") |>
      strsplit("#|[[:digit:]]") |>
      lapply(\(x) x[nchar(x) > 0L])
  } else {
    strsplit(x, regex, perl = TRUE)
  }
}

split.symbol.character = function(x, rm.digits = TRUE) {
  # Perl is partly broken in R 4.3, but this works:
  regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
  s <- strsplit(x, regex, perl = TRUE)
  if(rm.digits) {
    s <- lapply(s, \(x) x[grep("[0-9]", x, invert = TRUE)])
  }
  s
}

mol <- c("CCl3F", "Li4Al4H16", "CCl2CO2AlPO4SiO4Cl")
mol10000 <- rep(mol, 10000)

system.time(
  split_chem_elements(mol10000)
)
#   user  system elapsed
#   0.58    0.00    0.58

system.time(
  split.symbol.character(mol10000)
)
#   user  system elapsed
#   0.67    0.00    0.67

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