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#' Extract optional argument
#' @param tex_lines A character vector reading from a LaTeX document.
#' @param command_name Name of command (without backslash)
#' @param n Which optional argument to extract.
#' @param by.line Should the output be one row per command (\code{FALSE}, the default),
#' with extracts concatenated via \code{paste0(..., collapse = "")}
#' or one row per line per command?
#' @export
extract_optional_LaTeX_argument <- function(tex_lines,
command_name,
n = 1L,
by.line = FALSE) {
tex_lines <- strip_comments(tex_lines, retain.percent.symbol = FALSE)
char <- char_no <- line_no <- NULL
parsed_doc <- parse_tex(tex_lines)
nchar_command <- nchar(command_name)
command_split <- strsplit(command_name, split = "", fixed = TRUE)[[1]]
sk <- seq_len(nchar_command)
# Find the location of each command
nchar_command <- nchar(command_name)
command_split <- strsplit(command_name, split = "", fixed = TRUE)[[1]]
sk <- seq_len(nchar_command)
# Since LaTeX gobbles whitespace following a command, we must
# gobble it to detect the location of the command. The information
# we need is the char no, so it's okay to discard the rows, but not
# to parse the document without whitespace.
parsed_doc_no_ws <- parsed_doc[grep("^\\S$", char, perl = TRUE)]
# Add columns looking back
# Where we get a hit across all rows, that's the GROUP_ID to capture.
# Must go forward because optional arguments may confuse if we look behind
# braces
chars <- .subset2(parsed_doc_no_ws, "char")
# For each character in the command,
# check whether the k'th position back
# matches the k'th character in the command
# Idea is to melt the data table so that variable K should have value command_split[k]
# Fairly quick and avoids standard evaluation ;-)
for (k in sk) {
set(parsed_doc_no_ws, j = as.character(k), value = shift(chars, n = k, type = "lag"))
}
backslash <- NULL
set(parsed_doc_no_ws, j = "backslash", value = shift(chars, n = k + 1L, type = "lag"))
shift_char <- command <- command_no <- NULL
# Unlike extract_mandatory, we only care about '['.
candidates <-
parsed_doc_no_ws[char == "["] %>%
.[backslash == "\\"] %>%
melt.data.table(measure.vars = as.character(sk),
value.name = "shift_char",
variable.factor = FALSE,
na.rm = TRUE) %>%
.[, list(command = paste0(rev(shift_char), collapse = "")), keyby = "char_no"] %>%
.[command == command_name] %>%
.[, command_no := .I]
molten_parsed_doc <-
melt.data.table(parsed_doc,
measure.vars = grep("^OPT_GROUP", names(parsed_doc), value = TRUE))
if (nrow(candidates) == 0) {
out <- data.table()
} else {
.group_id_noms <- grep("^OPT_GROUP_ID[1-9]",
names(parsed_doc),
value = TRUE,
perl = TRUE)
GROUP_LEVEL <- id_at_group_level <- NULL
molten_parsed_doc <-
parsed_doc %>%
.[, .SD, .SDcols = c("line_no", "char_no", "char",
.group_id_noms)] %>%
melt.data.table(measure.vars = .group_id_noms,
variable.factor = TRUE,
variable.name = "GROUP_LEVEL",
# NA values correspond to zero groups, which we can exclude
na.rm = TRUE,
value.name = "id_at_group_level") %>%
# Rely on factor.
.[, GROUP_LEVEL := as.integer(GROUP_LEVEL)] %>%
# Choose the highest group number
setorderv(c("char_no", "GROUP_LEVEL", "id_at_group_level")) %>%
unique(by = c("line_no", "char_no", "char"), fromLast = TRUE)
char_no_min <- char_no_max <- command_no_t <- target <- NULL
# Must be outer join
candidate_char_ranges <-
candidates[molten_parsed_doc, on = "char_no"] %>%
# Only include NAs after the first command
.[cumsum(!is.na(command)) > 0] %>%
.[, .(char_no_min = min(char_no),
char_no_max = max(char_no),
command = return_first_nonNA(command),
command_no = return_first_nonNA(command_no)),
by = c("GROUP_LEVEL", "id_at_group_level")] %>%
.[, command_no_t := fill_blanks(command_no)] %>%
# When command isn't NA, that's the correct GROUP LEVEL and
# the correct id_at_group_level for n = 1. For later arguments,
# we just need to increment the id at group level (because it must be
# the relevant argument).
.[, target := and((id_at_group_level + 1L - n) == first(id_at_group_level[!is.na(command)]),
GROUP_LEVEL == first(GROUP_LEVEL[!is.na(command)])),
by = "command_no_t"] %>%
.[(target), .(command_no = command_no_t, char_no_min, char_no_max)]
if (nrow(candidate_char_ranges) == 0) {
# Under this condition, the nth argument of a command
# has been requested, but is not present
out <- data.table()
} else {
column <- NULL
column_by_char_no <- parsed_doc[, .SD, .SDcols = c("char_no", "column")]
extract <- NULL
out <-
candidate_char_ranges[parsed_doc,
on = c("char_no_min<=char_no", "char_no_max>=char_no"),
nomatch=0L] %>%
.[, .(extract = paste0(char, collapse = ""),
line_no_min = min(line_no),
line_no_max = max(line_no),
char_no_min = min(char_no_min),
char_no_max = max(char_no_max)),
by = c("command_no", if (by.line) "line_no")]
if (by.line) {
out[, c("N", "I") := list(.N, seq_len(.N)), by = "command_no"]
out[I == 1L, extract := stri_sub(extract, 2L)]
out[I == N, extract := stri_sub(extract, to = -2L)]
} else {
out[, extract := stri_sub(extract, 2L, -2L)]
}
}
}
out[]
}
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